make a list of all the things you do for him. like, are you the one to encourage him when he's feeling down? you do errands for him to save him the time and effort? (even though you both work - but you probably do both your own and his errands.) you raised his kids. (ok, they're your kids too, but probably you put a lot more work than he did into taking care of them when they were young, being there for them at all ages, even doing things for them now that they are at college. and he didn't do those things, or not as much, i.e. he gets the benefits of fatherhood without having to do the work.) you give him respectability in the community (he is a "happily married man" not a divorcee.) and you could probably add a lot more to the list. just make a list of why he would be a fool to leave you. even if you don't need it right away, it will do wonders for your self-esteem. and if/when you need it, you will have an answer for him.
and, what does OW do for him? probably very little.
