OK so he's trying 'nice' and has apologised. It won't last. He will not change overnight like that - a violent man needs years of counselling, CBT, experienced help to overcome a violent nature. If you are swayed by it, if you go back, he will think that is all he has to do. Next time he hits you, or breaks a bone, all he has to do is apologise.
Words are cheap. Look at his actions - do you think he can change? Do you think he will suddenly start being a calm, loving person? Do you think you can have a life with this person, and never again feel like you are on tenterhooks, waiting for the temper, the sudden mood-change, the 'because-he-can' punch?
(He's tried 'nice' and I assume 'threats and bullying' - it'll be 'suicide threats' or 'making you out to be mad or a bad mother' next, guaranteed.
It;s no way to live, Happy. And if you've read the 'relationship' boards on here, you will know how much it affects you dc, even if they never see a punch, hear a raised voice. It still affects them - because it affects you. Think about how you (and him) will be raising them, what you (and him) will be teaching them.
And, Sorry i don't mean to scare you, but if SS know that they are in a violent household, they will be keeping a close eye on you and them. (and so they should)
Also (again, not wanting to scare you!) have you seen this thread ?? Worth seeing - in fact, everyone shuld have watched the show.
You know what to do - you are already doing it. Stay away from him, keep your dc safe.
Don't talk to him, it will only weaken your resolve. No-contact, untill you are safe and settled.