well, the short answer is yes of course people can change, but in your situation, I would be very, very hesitant.
I think change usually happens either through growth and maturity over time (I am not the same person I was 20 years ago)
Or through a significant event that makes people re-asses who they are and what they believe in. (which could be the case - your splitting up could have made him take that step)
But I don't think it is that common, and I am not convinced that it is possible in a long relationship which has had unhealthy patterns for years. That sort of change would require massive changes of habitual behaviour. I would be sceptical that he could have done this on his own. And even with help I think that it would be very easy to slip back into old habits.
You talked about mind games - that says more to me than any assurance of change.
I wouldn't like to say never, but it does seem unlikely.
I believe that people can change, but agree with steppemum that you need to be very, very hesitant. You need evidence - both of the change and of it's likely durability. What has he actually done - counselling, therapy groups? Or is he just making assertions? 6 months is quite a short time for certainty, really. Do mutual friends see a real difference I him? Are you still in touch with his family - can they see a difference, or at least confirm that he has actually done stuff to work on himself?
Also, if he has changed, it's like a new him - you need to get to know him again, like in the early days of dating. Yu need to go much slower than ordinary dating, as you know so much more about his capaci to hurt you. No need to see (and assess) what he's like in a range of circumstances, over time, and including ones in which he showed his worst side before.
But before you do any of that, you need to pause for a bit longer - have you really thought through whether you want him back and why? How has life been without him around?
yes see what youre all saying. Mind games as in EA to some degree, very critical, never felt as if i could be myself in case he was upset etc.. He has done no counselling/therapy, he has no family and we do not really have many mutual friends to ask. This is all what he says he has done or is doing. Life without him is peaceful and i am finding that i enjoy the freedom, but there is this part of me that says maybe i should give him another chance..