Donkeys - its not for me to answer on behalf of the OP, but she has said in previous posts that he is an unemployed professional. I imagine that this could be the "thing" that has caused his change? I could be wrong. Maybe there are other factors, unemployment can = financial difficulties and that is a time bomb right there. (i speak from experience). So yes, his reaction was completely disproportionate to what the OP actually did "wrong", however it could have been a straw that broke the camels back scenario. NOT that I am excusing his behaviour in any way at all.
The problem with that explanation is it doesn't change anything for the OP because the man isn't stepping up and recognising he has a problem in the first place. He needs to hold his hands up and say "look, im sorry, i am feeling under pressure because.......please help" He isn't doing that - maybe he is embarrased? Maybe his head is in the sand? Or maybe he is just an arsehole.
If i was the OP, i would be expecting him to get help, this is what happened to me, i was reacting violently to my DP, he wasn't perfect by a long way, but i recognised MY problem and sought help. Over time, we have managed to put that time behind us and we are happy. I don't think my DP was ever scared of me, scared FOR me, but not scared OF me - the OP feels uncomfortable and scared around her DP, that is not good.
The thing is, he will be wanting this to go away now - that was on Sunday, whats done is done etc. Yes, it can't be undone but he CAN take steps to reassure the OP that when he says it isn't going to happen again (i don't know how he can say that!) it wont, and he will get help or demonstrate his sincerity.