"He had told me before that his counselor recommended not *quitting* but *moderating* his drinking."
Either he is lying, or his counselor is an idiot, IMHO.
"I promised this man that I would always be his friend but he can not accept the relationship on a friend basis and makes repeated promises about what will change if only I will consent to a further relationship."
"I have heard promise after promise that if I will just commit to the sort of relationship he wants, he would have every reason to stop drinking and he will never subject me to any more of the tirades."
Sounds like manipulation to me.
My advice would be to run, not walk, from this dude.