I think the biggest issue with your DBing efforts is that you did these things in an attempt to change how your ex was going to act, and expected him to be different instead of doing these things strictly because they were going to make you a better person and although you might not get the result you wanted - you would get the result you needed.
I have been divorced for 4 months now, and I didn't have much choice as my ex initiated the proceedings. She is still seeing the OM (I don't try to focus on it, it just goes on next door) and I just don't worry about it. I have noticed that he has been cheating on her with another woman when she is not around - but it really isn't my business any longer.
I'm raising my two sons and have joint custody of my daughter, and basically filling up the time I used to spend worrying over my ex and the OM with the kids.
My boys play football now, and I spend most evenings at their practices, or at the games. I don't really date, though I did go through a post-D fling thing.
The important thing is to do things to be happy about yourself. If your ex comes back around, that is fine. If not - that is fine too. You do what you have to for you and your son to be happy, and things will be alright in the end.
I live about 4 hours from my family, so I kind of know what it is like to be alone. You have to be superwoman for your son. Don't lean on him for emotional support.
"You can't reason someone out of a position they didn't reason themselves into."
