Gotta agree %100 with Kent...the ball is in HIS court now-you cannot make this too easy for him.
If it is too easy for him he will not see the value in it, in you. He might see you as a push-over which would cause you to resent him and him to withdraw...a vicious cycle (am in the midst of that myself and it ain't too much fun).
It is OK to commiserate with him about his sense of loss over not being able to be with OW anymore...but you ALSO need to let him know-in a loving way- that you are hurt too and he has to understand your feelings too and that the only way he's gonna get past it is to END it with her...PERIOD. Be strong and be there for him-but not too much...you are not a doormat!!