S., It looks like you have heard most of what I was going to say. However, on a legal standpoint, you can't do anything unless he has had no contact with your son for 2 yrs, that's no support, not visits, no birthday cards, etc. And then there is a whole series of things that you have to do.
I feel that you need to stop calling and arranging things, if he doesn't come around, then he is only hurting himself, and you are not to blame. At this point, when you push them together, you are only hurting your own feelings. Why do you have to stay when they are together(I personally would want to since he doesn't sound like much of a winner) but it sounds like he wants you to? Make sure that you are pushing them together so that you don't feel like a failure in picking him in the first place, this is the wrong reason.
Also, find a family member to watch your son (maybe even his dad's family) and take some time off. I don't recommend going out to the bars (that is not the kind of people you need to meet right now), but do some fun relaxing things for you... go to a movie with friends, get a message/pedicure, join a knitting circle, go to a scrapbooking event, go to yoga classes(my personal favorite), go shopping, or just go sit in a bookstore and read for a couple of hours (you don't even have to buy anything), check out your community ed brochure for dance classes, pottery classes, etc.
You need some time for yourself or you will burn out.