Hey there,
Harshness is not my intention here.
Ill make a stab at why he does not seem to be 'getting it' I have been there and this comes from experience and compassion.
By taking his calls, you are keeping communication open with him. To the alcoholic I left, this meant the game was still on and I was still able ot be manipulated or interested in negotiating.
I got calls at work too, I started hanging up as soon as I heard his voice. When it persisted, I notified my employer, to save MY As
I dont have children, so maybe the party would be something I would invite him to. I highly doubt it, but I dont have the experience in that arena. I am wondering why he cant just have his own time with the kids and needs to spend time with the kids, in your presence?