FA ex seeking attention? Or has he moved on?

There's so much assuming going on here, filling in blanks, and doing so in the most negative way towards yourself. You've created an entire story, and it's one that compares yourself to others, devalues you, and leaves you jealous over, again, what is a story you're telling yourself. Do you see how it's your brain trying to repeat past patterns and tricking you into positioning yourself in the worst possible light?

You have zero idea what's going on with him (social media isn't all real), you don't know if he's done any of this at all with you in mind besides perhaps mindlessly liking your tik tok (I'll give you benefit of the doubt for your instincts on that one, he's probably not thinking about it too hard and simply reacting to seeing your post in front of him but at the same time may be fishing to ease back into feeling like you still have some distant connection and you're still there for him, insecures do that passive-aggressive stuff. I do not think he's flaunting other women at you, though, and if he is it means he's got the emotional maturity of a middle schooler).

You know seeing his social media makes you spiral, so you've got to just keep hiding and blocking the loose ends as they come up. But really ask yourself why you're doubting your actual experience, the one where he treated you like crap, and making up a virtual one in which you're the "loser" without worth? You get to define that for yourself, so why are you choosing to paint yourself in such a mean light within your own narrative? What would you tell a friend who was in your position and doing that?

ahh there’s a lot to cover, so I’ll reply collectively in one comment. Sorry for the long comment ahead.

I will preface I do appreciate the feedback and I’m still taking some time to absorb it all.

I’m hoping these will give a bit more context as to why I feel/think this way, but I acknowledge that my thought patterns aren’t healthy and I do need to work on them. I apologise if any of my responses sound standoffish and messy. I'm still a little emotional.

1. Thinking I have influence over him - I suppose the reason why I feel this way is because he's had a history of doing this over social media. When we were together if he was frustrated over something and had no one to go to, he would make posts on social media but be very vague about what exactly he's talking about.
It was very frequent when we first broke up and the timing was always when I posted a story of my own just going about my business, he would see, feel some kinda way and then he just must post something to get it out of his system.

2. Him liking my TikTok or any social media post – we had a big fight about this after our breakup and at the time I explicitly said to him, if we want to stay connected on social media then please don’t like or say anything to me unless he wants to reconnect and talk properly. His response was "Fine, I won’t ever fucking like anything you do ever again. I don’t give a shit anyway we are done talking. This is your closure and I’m moving on" and that was that.

3. Him flaunting women around him - after the breakup he has been very active in socialising and meeting new people. Girls did flock to him and when we replied to them on social media it was always very flirty. He went as far as to gloat on one comment saying “Girls would never find me boring, they love me”. He's never had a history of doing this in the past, even before we met. He had a habit of keeping his distance with women he has no interest in and majority of his friends have always been male up until we broke up.

4. Blocking and unblocking - he was the first to throw this out in the open when we broke up saying, if we ever get into an argument and he blocks me, then don’t ever dream of getting unblocked. Ever.
He’s also the "out of sight out of mind" type, even when we were together, so I honestly thought he wouldn't even remember or think about me after the blocking charade we went through.
This is why It makes me wonder what the reason is behind the unblocking, I just have a nagging feeling that he knows what he’s doing and he’s doing it to get attention but never taking the responsibility to reach out and talk properly.

I know he treated me terribly when we were together, so the fear of him dating (A) almost doesn’t make sense. I do acknowledge that the following part is me assuming but I’m having a hard time thinking otherwise, I have calmed down a bit but there is still some ruminating going on.
The reason why I feel like he would be different with (A) is because, when I was with him, he was broke and I was always expected to be hyper-independent, I had to be there for him emotionally and help him through his ups and downs of running his studio whilst worrying about my own future. I paid for gifts, flights, accommodation just to keep our relationship going but he never one offered to do the same. when I had needs, he blamed me for being too much, dragging him down and being a liability.
Now his studio has taken off literally in the span of 6/7 months, business is booming, he is comfortable and stable. He won’t ever require (A) to be hyper independent about anything, he won’t ask her to help him, he could probably spoil her as well.
I just feel so bitter, it felt like I poured my heart and soul into being there for him during the hard times, but (A) just came around at the right time and the right place to enjoy everything that I never got to have. It feels like the biggest slap in the face.