Re-read DR again. You are doing things that are pushing him away. Stop it.
DON'T read old letters- it's really hard, but you just get into wallowing in your pain, and not thinking about what you need to do to take care of yourself.
DON'T involve his family, even if they are calling you. That is going to p*ss him off and push him away. Just tell them you are doing the best you can to take care of yourself, and leave it at that.
DON'T get into the "YOU did this, YOU ran off" blame game. Again, it will just push him away. If he expresses angry emotions at you, just say "I am sorry you feel that way". STAY AWAY FROM RELATIONSHIP DISCUSSIONS! You are not speaking with a rational person!
My DB coach told me to use this tool before I say or do anything to my partner: "Would K say that what I was about to do or say was going to push her away, bring her closer, or just be neutral?". Good tool for you to step back and analyze your interaction before you open your mouth.
My partner has left me for OW. We had a 16 year relationship that I thought, and most friends agreed, was great. Now, my partner tells me that we had issues that were unresolved from the beginning of our relationship and she got tired of trying to get me to fix MY issues. She wants me to acknowledge that we are not breaking up because she is involved with someone else, but that our relationship was so broken she didn't want to try to fix it anymore. Funny, but the month before she went to IL for the new job, she ASKED me to buy her a new wedding ring (the stones in the old one were broken), so everyone in the office would know she was married!
I could remind her of this, and of all the good times we had and love we shared, but she doesn't want to hear it now. Nothing I say will change her perspective until she is ready to change it, and that will only come with time. I suspect it is the same with your H....
Me: 50; Wife: 48 Gay; civil union in NJ no kids M: 15 years, together 17 Bomb (OW) 2/09 (EA 3mos/PA 3mos) ILYBINILWY W out of house, w/OW, in separation talks, nothing filed