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".
(no reason to read past first page where is aim is conformed)
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)