Just don't open the door.. or answer the calls. If you have kids together (like I do) it's harder.. get a communication book going. No actual verbal communication or physically being in the same room.
...or...you could say,"I"m done, I don't feel like this is working between us....yea. Just did that this morning. :) fun fun
Tell him that you have a confessions to make and that is a couple of years ago, you were not in the mad house for nothing
No way is going to be nice in the state he is in
But im afraid thats not your problem.
Anything you say nicely is going to sound mean to him if its cutting him out.
Hopefully he will greive and then finally realise it was him and slowly learn to be a stronger person. If he doesnt thats unfortunate but nobody can get someone to that strong point but themselves