That type of quiet rage is so eerie, especially knowing he can misplace his anger and direct it at you.
Would it really make a difference as to why he was directing his anger at you or why he was cruel to you?
I know you're scared and suffer from low self-esteem. However you need to be your friend right now even if/when those bouts of self-loathing come.
Tell the truth to safe people IRL. Some will believe and support you, some may not. Do not keep this a secret seeing as you're already on your knees.
LTB seems like this huge and massive goal right now.
So get some sleep when you can. Enjoy those nice moments with him when he's in the good guy mode. You don't have to hate him. Keep calm and advocate for yourself when you can, don't keep his sordid secrets to yourself.
This is very hard. If I could just snap my fingers and help you LTB, I would. Still, talk to someone IRL about this. Enjoy the good times when they come but be rational and seek support.
You don't have to do it all at once. But don't keep this a secret, hun. We're here for you x