Thank you all for your support and advice.
I don't want to get too detailed here, but I've taken a number of the steps you all mentioned - and good thing too! I didn't think he had it in him, but he certainly did. Maybe it is his gf's influence.
I also found a message board for his fantasy football league that he does with his brothers. They said some very mean and hurtful things about me and he agreed AND admitted to his affair. So, I've printed those out. I was also able to print a ton of other documentation about our finances, debts, assets, etc.
I'm just trying to enjoy myself right now and do things I haven't been able to in 10 years -I changed into my pjs as soon as I got home, ordered pizza for me and DD, didn't worry about doing the dishes right away, talked to my girlfriend without having to go outside, let DD sing the song she learned at the top of her voice, put on what I wanted to watch on TV and a bunch of other small things. I miss the guy I thought I loved, but I don't miss the one he became. Its funny, i thought I would be much more upset when he finally left. Maybe I'm still in denial or too busy with the details, but it's okay right now.
I also made appts with several attorneys and my physician - I figured if he's been sleeping with her, I better get myself checked out.
So far, DD is clueless. She know H is not home, but figures he's just on one of his weekend trips, which he made quite frequently. I haven't talked to her yet about the permanency of the situation. She's still upset about the whole school incident.
Thanks to the PMs for support and the offers of advice, articles and prayers - I'll take it ALL right now.
Also, as far as custody, does any know if he will certainly get joint? I have a chilling voicemail from him from 6 months ago where he calls our DS "demon-spawn" and that if I didn't get home right away (I had left for the gym 30 minutes before the call came in. I haven't left him with DS alone and awake since), he didn't know what was going to happen. Do you think that can be used in court? I really don't want him to have these children alone at all. He can be vicious. At least now, I can intercede and make amends right away. Part of me thinks he won't go for custody. the other part thinks he will, out of spite and because of his parents.