I completely understand . My husband attacks me with verbal abuse as well and it seems to only be when he drinking too. When he's sober he's amazing. Its when he starts drinking that is the problem.
I've had the same experiences I stay at home with my 2 year old and when he drinks he says things like I work and you don't bla bla bla and I should do this or do that. I'm not right by staying but I've had this denial that I can "fix" it . This denial continues and I am working on myself so I can't say that his mother was bad for being caught up in the abuse/alcoholism. Being abused isn't a choice its a mental defect by force. A bully on the playground is no different than one in the home. Abuse causes people to suffer emotionally and mentally and in some cases physically not that a person can't or won't leave but the cycle is what keeps them there. As someone who is familiar with psychology Iwould think you would know this .
Which us why you me and most every partner in abuse cases stay. Can my alcoholic husband change? I don't know he must first change his drinking and change himself . Can your boyfriend? That's up to him.
My ah also grew up in a family where abuse was present and his mother is Christian and was /is in denial and despite what she did or did not do....that was the past and this is now. If you cannot forgive forget and move on about his mother abduction what she did or didn't do then how can you expect him too (after all if you dig into it. I'm sure his problems are not only with his father but mother as well) he needs therapy to surrender himself to life and moce on.
Abuse is a cycle not just the one your on with him but one where he was abused and he abuses so will your children if any result as a victim.
To move forward you must tell him it is not acceptable with your actions not words ie leaving (I will be following my own advice as well) he needs to face himself and what he's doimg. He won't if you stay with him as you arevso much easier to assault with hate than himself .
Good luck