Originally Posted by
Pelican 
Tell him you changed your mind, and want to end the relationship. period.
no long explanations needed. YOU change YOUR mind.
ITA with this suggestion.
I found these boards five years ago when I was trying to end the relationship with ExABF. Thanks to the wisdom of posters here who had gone through the same thing, I was able to tell him I was ending the relationship and establishing boundaries in the process...he was not to contact me. Of course, he tried...but I was firm...and that WAS the hardest part.
The A will always find fault with you and make you the reason for the A's behaviour. If you go NC, the A has to find another scapegoat/enabler. Freedom!
And yes, when I read your description of your ex as a RA, I thought "dry drunk".
Stay strong and make yourself the priority in your life.