Suddenly FA in middle age. Am I broken?

I'm sorry you've gone through a lot of pain and are still in a tumultuous space. My opinion is, all of you (you yourself, you current partner, and your therapist) are somewhat right.

Your partner is probably correct that you are not ready for what she wants at this time, and that's okay. It's incompatibility unfortunately, but it's okay because life stage timing and being on the same growth page in regards to emotional maturity is just a part of adult and committed relationships. It doesn't mean you don't care enough, and I'm a little surprised she would say that if she understands attachment theory. Maybe you haven't learned to care enough about yourself quite yet, but it's not about her or how much you care about her. There's way more than that at play.

Your gut is saying something is wrong, that's also correct. But finding the answer to what's wrong and causing the void won't be in other women. Comparing and contrasting a bunch of new partners won't teach you what you need to know on its own because that keeps the focus on others when the core problem is not with your partner (assuming your current partner really is emotionally healthy). The problem is inside you and your relationship and connection with yourself. You'll run into the same problem over and over by exploring and focusing on lots of women and situationships without some other plan of inward focus and work happening at the same time. With this approach of lots more dating for its own sake, you'll also inevitably meet someone more avoidant than you who will make you feel totally "in love" and end up in another toxic mess that exacerbates the existing underlying issues you haven't dealt with yet, because that is just the way relationship dynamics work for FAs who are struggling in the ways you're struggling right now. That will delay healing even more and add more layers and attachment wounds to heal.

Which brings us to what your therapist said. The therapist is right that you need more time to heal. But I don't think it's going to work to focus only on healing from your toxic ex. You need to actually go way further back than that, and heal something else that happened before, something that created an emotional state within you that primed you for being attracted to someone toxic and then staying with them. That is where the void is coming from, somewhere before your ex. It is within whatever circumstances caused your attachment wounds and FA attachment style in the first place, which your ex I'm sure did not help in any way but which certainly existed before you met.

You're doing yourself a disservice to say this is "just" FA or "just" deeper wounds from your marriage. That's minimizing the underlying issues, though I assume you're doing that because you already know how painful and difficult they are to unravel (which is why the idea of just dating a lot of other people is way more appealing and sounds easier in theory!). Minimizing them makes that pain and growth easier to avoid. But you need to decide for yourself if that void you feel is painful enough that you need and deeply desire to change or not.

My recommendation is to talk more to your therapist about what happened in your life before the marriage and how you can heal that first. Then move on to processing the marriage with the better tools you're learning through therapy. Scale back on dating, and when you do date, be very honest about only being ready for casual or short-term situations (and don't try this with women who are anxious attachers because it will become a mess and they'll try to turn it into a real relationship that's nothing but push-pull). Tell your partner that she is right you're not ready, though it's not because you don't care enough for her, it's your baggage. But that it doesn't change that the timing is off. I think you should make a clean break with her for now, no contact and no distracting each other. Which sounds scary, but who knows where you'll both be emotionally in 6 months, and if you've made some healing progress and overcome the void on your own, maybe things can be different. If they can't be and reconnection doesn't happen, we have threads here that there are good partners who still exist after age 35 (even if there are fewer), and there's no need to add to your fears by having a scarcity mentality. You'll meet the people you're supposed to when you're ready. Like attracts like, and people seeking connection will find each other even later in life.

This is exactly it. It will feel very uncomfortable to dig into, but FA is very commonly a natural response in a child experiencing familial enmeshment. If you're not familiar with the term enmeshment, pop it into an internet search and you'll get a ton of information to start off with. Combining one parent enmeshing you with having an extremely insecure avoidant and distrustful detached other parent, and you didn't have proper modeling for a healthy sense of self, sense of boundaries, or learning interpersonal relationship skills. (One of the other top contributors to any insecure attachment style is having an adult attachment figure around in your childhood who has a personality disorder, though I'm not sure how pathological your dad is from your description).

Definitely discuss with the therapist. But don't be surprised if those avoidant defense mechanisms kick in and you start feeling uncomfortable in your sessions. That means you're getting somewhere, because all your subconscious conditioning was to avoid all this childhood pain and discomfort that you couldn't process at the time. To live with it, you needed to push it down somewhere. As an adult, you get to make the choice to recondition your nervous system and learn to process what happened, though it is not quick. You're already seeing that labeling and being able to verbally identify and describe what you experience helps. I had to understand what happened in my childhood so I could re-write my narrative in a more fair and realistic way that was also compassionate towards myself... which allowed me to depersonalize and also throw out the dysfunction I learned from others (and still see in them since they haven't changed so I need to continue to hold boundaries and depersonalize and not let an old "script" given to me by others define me).

I once found this video pretty interesting. It's an interview with Neil Strauss, who wrote the book The Game (the pickup artist book) when he was extremely unaware FA and then wrote the book The Truth about his process coming to terms with his insecurities and fears and earning secure (though he doesn't say this in attachment style terms). The video discusses enmeshment and thinking about change in a unique way. I liked the "turning the spoke" description. (You can skip to 11 minutes in to start.) youtu.be/aDwYlZAE3Q4

Some suggestions on how to work with desorganised attatchmentstyle.

A toxic marrige can push you into some desorganised attatchmentstyle/trauma. 
By being in a toxic relationship you are going to live in an alarm condition state in the relationship and after the relationship has ended. Shock trauma and unsertanty can get stuck in your nerveussystem.
jebkinnisonforum.com/post/29355/

jebkinnison.boards.net/thread/1073/healing-disorganized-attatchment-chock-trauma

Healing from the disorganized form of attatchmentstyle is at the deepest level of seerate the love / safe attachment from the threat.
Unfortunately, you can not talk or analyze this!!!!
It must be healed on all 3 levels: the mental, emotional and instinctive level!

REMEMBER: Healing on the instinctive level, must come first. It´s survivel energy! When your system is in survival mode, it overrules everything else that you might have learned - your logic and your emotions - and your lovelife!

You can try to find an attatchment therapist who is also educated in somatic experience. Maybe you already know about SE ?
And who knows what it means to be around people with personality disorders ect. (your body will show)

When you get into a relationship that is more healthy then there is more room for the trauma whirl wind to make noice. People often get confused why they are suddenly having theese “wierd” reactions when they have found a secure partner. Theres a post about this in the healing desorganized thread.

Theres a thread called healing a broken heart and how to live with an open heart in the general forum. Maybe you havent healed enough from your toxic relationship.

jebkinnisonforum.com/thread/1169/healing-broken-before-changing-partner

Don't be astounded about how poorly the two of you communicated, even when typing carefully over text, as text is a terrible way to communicate in a relationship triggered or no. That just stood out to me as texting seems to be the main form of communication in insecure or toxic relationships, but it's just a supplemental form of communication in available, secure relationships.

Anyway, sorry to butt in here, it just stuck out to me. Communication is huge, and texting is inadequate and even dangerous for relationships except for minor stuff or things also communicated in person.

Honestly, so many insecure relationships would crumble almost immediately if it were required the parties meet face to face to truly connect and also to resolve conflict. Insecure entanglements thrive on unavailable, drama filled communications via text. Typing into a device is the worst way to go if you want a real, intimate, vulnerable and meaningful connection with a true partner. But if you're looking to sustain an unhealthy narrative, block intimacy, and leave a whole lot up to imagination text is the way to go!