neph-- The 5 love Languages book is awesome--but we can't apply any of it while there is another person involved. We currently do not have a R, as OT would tell me.
Concentrate on you...you have been doing incredible. There is also a lot of info about Adult Children of Alcoholics (ACOA) out there, and you may find it eye-opening. We do take on much more of the blame than we really deserve.
And you did the right thing with going legal. I filed the next day after discovering the A. If he could lie so blatently to my face for so long, I couldn't trust anything that he promised he would or wouldn't do. His guilt worked in my favor by doing it early--he agree to the amount of $ I needed to keep the household running, and a no-contact clause between OW and the kids. I also agreed to not expose the kids to anyone I were to meet. This pendente lite motion stays in place until the court date in Nov, and then it can be extended. It helps by also showing precedence--he has been paying x amount of dollars, keeping the no-contact, and the sitch hasn't changed "in a substantial way."
I HATED having to file--but I had to protect the kids. Even with that, he tried to reduce the support and eliminate the no-contact on the day the papers had to be signed (it is something that both parties have to agree to, if it is beyond what the court would have ordered). We had to go back again a week later, after I pressured him into reminding him that he had given his word.