Need Clarification

Some questions:
1. Why didn't the black guy set up Van Damme, too, if it meant more money from Polo, who said he wanted the man who killed his brother, or he wouldn't help get Flint? He said for the right price, he'd sell out anybody. And if he hadn't set up VD, what was the ''falling out'' he and VD talked about later in the movie?
2. Polo's help in getting Flint amounted to just being bait to get Flint to City Hall? Flint went there ahead of time anyway, just hoping to get Polo, so I don't see how Polo helping was really necessary.
3. What information did Polo get from Flint's partner, who was tortured till he ''sang like a sporano''? Just the location of Flint's wife out in the country?
Overall, a very good movie in my opinion! And, thanks ahead of time!