My advice would be very careful before making the decision to marry him. My abuser was very Jekyll and Hyde, he could be the funniest person you could meet, making promises of all the things he'd do for my mother and me, and go out of his way to help people (once he spent until 2am fixing my aunties car even after they'd gone to bed), or he could have the most DEMONIC anger and scream for half an hour none stop. He was also abused as a child and had nobody.
It sounds as though he has some serious trust issues, that could go a number of ways, including him becoming manipulative or controlling. A lot of abusers do what they do because it gives them the power and control they've never had, they can only 'trust' someone if they manipulate everything the other person does. They can do the whole 'I have nobody, and nobody understands me but you' thing, and then say and do generous things, only to suddenly erupt into anger/abuse. That's to confuse you, so that when you think the anger was wrong, you remember all the 'good' things they did and figure they mustn't be so bad after all, it must be a phase, or an outburst only 'you can understand', so you stick around.
Of course all this may not be the case, but it is a possibility.
If you trust him and want to stay with him, he needs therapy. It could get worse over time, and any mistrust or hatred of himself he has will more than likely be put on you.