How late is too late to try? Two steps forward and many steps back

My ex walked out of our relationship 4 months ago. He was cheating on me with an emotional affair which has since turned into his rebound I guess (meaning they are still together but out in the open).
The break up was completely unexpected and his behaviour since then has been completely out of character (I never would have thought he’d cheat either he has always been vehemently against his cheating father).

My question is, is 4+ months too late to try getting him back? In the last 4 months I have dealt with/done these things:
Begged him once (way back in the first day) to try fixing our situation and asked him to stop seeing the affair partner while we sorted us out;
Had to live in our house (with him walking out and living with her) because I couldn’t afford to move;
Moved out of the bedroom immediately and slept on the air mattress in the spare room;
Had to deal with living with his brother;
Started therapy;
Said many things that I can see look very desperate but seemed like casual remarks to me at the time;
Tried NC without knowing but failing miserably;
Had to move out in 3 days because he decided he wanted to move back in with her;
Had our pet cats taken from me by him (he said they were his because he paid for them);
Had to hear him say many cruel things and not one apology about the whole situation;
Been told by him to stop contacting him (recently within the last week that is);

If there’s still a chance to get back together, how likely is a misstep going to push him further away?
My main concern is wondering if I’m too late to even start?

I hope this post isn’t confusing or anything and has enough of the right information to help me get a clear answer about my options.

How long were you two in a relationship? Do you own the house together? Are you living somewhere else now?

No I don’t think that 4 months is too late. I only started NC two weeks ago and that was 6 months after she wanted a separation. Since you were the one being dumped, and he said that you should stop contacting him, then you should cut him off completely. Keep doing the therapy, take up a hobby, join a gym, enjoy the company of friends and family. Basically just forget about him and focus on yourself.

It does sound like he is already in a rebound relationship so it may take several months before he will start missing you.