Re: eddie's first backer holding out on him:
I think each game is a new backing agreement as was mentioned earlier.
So if you agree to back a guy for 1,000 and he wins, the original thousand you put up never left your pocket, it's still yours to reinvest or throw away or whatever. The player 'owned' it during that first game, but no longer has a claim to it after that game ends. He can only play with his half of the money he won, he doesn't have a right to gamble with what's still yours unless you agree to it.
I think pretending the money doesn't exist just to avoid the awkwardness was a little squirrelly. Better to let eddie know exactly why the well's run dry so that he can think about it in the future. "I didn't get staked because I was drunk" is a better motivator than "I didn't get staked cuz he ran out of cash".
And yeah, burt's move was just muscling him. I guess you could argue that burt steered him to the 2nd set with fats, since eddie couldn't have gotten a stake without burt's help, but under the circumstances they were more than square, which was eddie's argument too.
I think the drama of the ending was a good thing, it adds some yin to the yang to make the movie that can appeal to everyone, not just pool players.