I don't really want to sound harsh, but your kids deserve better than this. You should sit down and talk with them, too. Your significant other/their father was abusive. They might not feel safe with him living in the same space as them again, even if he is on meds.

Give him and yourself some more time before you have him come back. Study his moods and how they fluctuate. Hell, take notes if you have to. But please, please think of your kids. That's so important. I wish my dad had talked to me or been more supportive when my mom became abusive. It would've made me feel a lot safer and made growing up a lot less difficult.

Best wishes.