1) I haven't seen many .us domains performing well in Google.Com so far. If the .com, net & org aren't available anymore, I would personally add a small word to the phrase (if that is available).
2) Yes, as a non-US resident you can buy .us domains (like through Dynadot). The terms say you can't though, but I did it and so far I haven't had any problems with the 4-5 .us domains I own.
3) That's what I would do