For various reasons we cannot kick him out of the social circle.
and yet, he is a thief. If he had taken to rooting through people's coat pockets and purses, would people be more willing to kick him out?
Actually, probably not. People are funny, aren't they?
I am scheduled to host one of the next activities which everyone knows is a social circle only event. I have attempted to contact him privately twice through different communication methods ... I know that he has received both messages asking him to call me but he has not tried to contact me. I will likely see him soon at a party but I do not want to talk to him there because historically he tends to react poorly. I do not want his drama to ruin someone elses party.
How do I bean dip this conversation so it does not happen at the party?
You say, "Oh, yes, Stealer, I did want to talk with you--but I'm in the middle of the party. We'll catch up right before you leave."
... He knows the expectations of the event I am hosting, so do I even need to remind him?
I would think that you do, especially since in the past, he has been successful in trampling boundaries.
How do I do this if he wont answer all my attempts to contact him? Can I just leave a message on voicemail?
yes, you can. Do it right after this upcoming party.
And I would start to say things like, "I'm not coming, because I get too frustrated when Stealer shows up and mooches. I used to be able to live with it, but he's essentially stealing from all of us, and I'm not going to be his victim anymore. So you are going to lose me for that event. Let me know if he gets uninvited, and I'll show up. I *was* looking forward to it."
Start letting this reasoning be known--drag it out into the open.
In fact it might be a good idea to pull a victim card on him about how you always end up covering for him and how you came to X event on a fixed budget but because you had to pay for him, again, you got short changed and how this has happened before and how come he never gets your back its not easy being you and you have have a budget and limited resources too and he's always taking taking taking and its just becoming way too much and how can he consider himself a friend and do these terrible things to everyone around him when you've never been anything but gracious and generous and now, now when you need a little compassion and understanding he's trying to be the victim, no no no you are the victim and he's sooooooooooooooooooo mean to not understand and not try harder.... Just go on and on, and get upset sounding and don't let him get a word in edgewise and lay it on thick.
And in fact, lay out this argument--because it is absolutely true, and not in the least exaggerated!!!--in front of everyone else.
When his name comes up, point out that he's not a very good friend, that what he is doing is stealing from people who are NICE to him!!