I'm sorry you had such a horrible relationship.

A few things popped out in your post.

1. Having Bipolar is not an excuse for him to put his hands on you in a violent manner, never !
2. Not all people with Bipolar act like he did, I am certainly not violent if I am not taking meds.
3. He lost his job and wasn't able to take his meds? Not sure where you live but, in the USA every county has a mental health clinic , so there is a way to continue on meds.
4. You and him had a bad ugly break up, it happens, most people go through it at least once.
5. Someone with Bipolar can react in many ways to changes in there life , good , bad indifferent. He is your Ex, doesn't matter how he reacts at this point.
6. You could spend years trying to figure out what went wrong and why. Pointless.
7. Regardless of who you date , someone with a mental illness or not or any variety of health problem ... Remember you deserve respect.

Don't settle , life is too short.