If you R, you have to have a big say in what R will be and what your new M will be.
Think about this: in a sense you sold yourself out by cheating. Part of healing is to stop selling yourself out. Another part of healing is to change from cheater to good partner, and when you're a good partner, you have to actively define and participate in the partnership.
Your H has to heal himself - you can't heal him. You have to heal you - he can't heal you. As your and his healing progresses, you can decide whether or not R really is the best resolution for both of you.
I'm as sorry as I can be that your cousin molested you. That's a gigantic burden to carry. It will be a lot of work to learn to put that burden down. I hope you find good help. If at first you don't, keep looking. 
The International Society for the Study of Trauma and Dissociation is a good place to look, and their website has a 'Find a therapist' feature. But even the therapists they list can be iffy or downright bad, so look for help, but be careful.
Yeah, I know that advice isn't a great confidence-builder, but predators hide in plain sight. I really wish I could tell you how to spot them.
*****
I don't know your BH, so I don't know if he'll follow through or if you will follow through yourself, but ...
my W felt worthless. She thought her A was unforgivable. She could not understand why I would want to R with her. 
I had some stiff requirements, and I couldn;t see why my W wanted to meet them.
Our MC was W's IC. Some of our MC time was me asking for reassurance that my W was committed to R. Some of her IC sessions involved her getting reassurance that I wanted R.
Our MC reminded us that every time we questioned the other's commitment to R, we always sid we were committed. Our MC told me that my W always expressed a commitment to R. As far as our MC was concerned, we sounded like we meant what we said.
So maybe your H isn't committed, but maybe he is. Whatever his level of commitment may be, though, it makes sense that you may doubt him.
 [This message edited by SI Staff at 7:13 PM, Saturday, November 1st]