Just a law student, so I don't know what the hell I'm talking about. Assuming you have the documentation to prove your claims (sounds like you do), then you have a pretty clear claim. If you did the work in Chicago, you should (I think) be able to sue in Illinois courts. You'll probably need to hire a process server or something like that. Check with the SC court clerk about these details.
1. Most likely outcome is he does nothing and you're awarded a default judgment. If he shows, you're ~100% likely to win, from what you're saying.
2. You need to take your judgment and get it certified in NY, then use NY courts to enforce the judgment. I have no idea about the logisitics of all this.
3-7. No idea. If you know any of the clients of the business, you can tell them what happened, but don't lie or exaggerate. Better yet, threaten to do this first, then do it. Also consider informing the NY AG or BBB or people like that.
Anyways, that's my take. I'd talk to an actual lawyer though, or the clerk of the SC court.
IL small claims