Ahah uh. Well i found that rather difficult to read but i think i understand it. Um, He obviously developed some issues on trust. And im going to guess that the majority of them were because of his parents splitting up. I mean divorce is a nasty thing to go through, he probably found his mom telling him stories about his dad he should never have known, and vice versa.. just because the parents can be spitefull. I mean I know one guy who found out that his mom was having an affair and his older brother wasn't actually from the same father.. so that is a HUGE impact.
He'll grow out of the trust issues, perhaps its just a phase. Best thing you could do is just monitor it, cater to his needs for now , make sure he doesn't do any really rash decisions. One day he will clue into it, we can only hope anyways. Also if you find he is in a relationship for a long time, and he might get feisty/restless over the fact that he's been with them too long, and they aren't suppose to be together , just try to convince him that he shouldn't do or say anything to make the other partner angry (thats probably what would happen).
That's just my two cents, i only read over it quickly. Also if you wanted to take it from another perspective, agree with him. And say "yes, there are only years or a certain time in which two people can be together. Some it will be 1-2 years... 1-2 months, perhaps just a one night stand. But did you ever think that there might be a 50 limit year on a certain relationship?" good chance.. if he's 20-30 years old (I know he isn't, hypothetically)... i mean they'll be 70-80.. good chance they won't live that long (sorry for being morbid) . .. . i'd say that is your best of making him realize this. I never even thought of it this way.. but it could make sense
Yay rants!