I'm going to permanently embed the term "jack-slap" in my vocabulary now!
I was in a very similar situation. After 13 years, I uncovered a mass of deciet and invited my AH to leave. He immediately responded with AA meetings, counseling, abstinence and the "But I NEED your support to do this." Well...he had my support for years and it didn't make a hill-of-beans-difference. If he can't do it on his own, then he can't do it at all anyway. (BTW - my AH stopped all of the above when, after three months, I finally got him to understand that there was no marriage to go back to and his reason was "Well, why bother now?")
My thought: if you want to leave, you should leave. It is not his decision and you don't need his permission. When I finally ended my marriage, I repeatedly told my AH that he had to let me go when he would cry and guilt me. Then I realized that I was talking crazy. He doesn't HAVE to let me go...I had to let MYSELF go. And I did. Viola!
I do have to say that I still feel some guilt when it comes to my babies. My oldest told me last night that he told his Daddy that maybe he could move back home on July 1st. UGH...shot to the heart. But as far as me...I feel peaceful and grounded for the first time in YEARS. And all I had to do was give myself permission. Sounds so easy, doesn't it? LOL!! Oh, if only...