It concerns me a lot that he doesnt want you to talk with anyone you have ever had sex or even been on a date with - that sounds like someone who is very insecure and very controlling.
My only advice is LISTEN to YOUR feelings. Dont ignore them, you have them for a reason. I am not saying dump him but you have to find a place where you are comfortable and happy and only you can be the judge of that. Sometimes we believe what we want to believe or hear what we want to hear, I am not suggesting you are doing this, but I also cant quite believe that his cousin bribed him into sex and he allowed it to continue for 5 years....it doesnt ring true to me. And if it was true shouldnt he running a million miles from this person regardless of the impact on his family.....what about the impact on him and his relationships.
Dont want to be a dark cloud but I am going to be..........something doesnt sound right and if it was me I think I'd be taking some big steps backwards.
Sorry Fifi