OK, I read whole thing, and based on his comments to you he came across as one that may have ripped off others in the past, so I took a look expecting to find previous douche behavior such as demonstrated in your aim chat logs.
I am playing at the moment, but a quick search seems to show he has had stealing issues in the past which includes ripping people off on P5s and Neverbeg/PartTimePoker where it appears he was Banned for stealing $57 in 2006 playing under the PokerStars name PornoStar69.
The P5s is a little hard to read because it is from old forum, but it is clear they are talking about your horse using aim "knapp2themax".
http://www.pocketfives.com/f7/must-r...ethical-82067/
http://forum.parttimepoker.com/make-...rnostar69.html (no reason to read past first page where is aim is conformed)
http://forum.parttimepoker.com/members/bigslick.html
I will look into more but at first glance it appears this guy may be a long-time thief from at least 2006
Looks like he is/was from Greenwood Village, (Co?)
He also briefly used FTP account: POKEHERSTAR06 so he
may be a multi-accounter as well
(confirmed this is same person OP staked)