I am, like, totally not a lawyer. As best I can do without going and actually looking things up (which means, of course, that this isn’t legal advice you’re getting, so don’t take it as such), here’s my answer:
Hypo 1: Probably not valid, because in this case you’re discriminating against persons of a particular national origin, which is, shall we say, frowned upon. “Not for export”, though, is A-OK.
Hypo 2: Sort of. Similar schemes have been used in the past. Recall that, until IE came on the scene, Netscape was free to education and government users, but private industry had to purchase it, according to the terms of the license. It’s not at all uncommon, so I hear, to make a consumer-level product for the masses but to state in the license that it may not be used for commercial purposes, and that commercial users must buy the “Business Edition”.
BUT, your stated scheme differs from the above in that you want to flatly deny a group of persons access to your software. I would say that you can charge them a higher price, definitely, but I’m not sure what a court would do with a “these persons may not use any form of this software”-type restriction. I’m inclined to say that it would be enforceable, but I’d have to do actual research to be sure.
Hypo 3: I don’t know of any cases on something like this, but as long as your discrimination isn’t based on his membership in one of those special classes (you know, race, religion, blah blah blah), you should be okay here.
Side-question 1 kinda got answered in Hypo 2 up there, so I’ll skip that one. Side question 2, I can’t answer without looking things up, but my gut reaction is yes, Billy Bob knew about the license restriction (or, at least, the law will treat him as though he knew about it), he chose to ignore it, he’s gotta pay the piper. Somehow I suspect, however, that you wouldn’t get $250,000 out of it unless you could show that you were damaged to the tune of 250 grand, even though you specified that amount in your license agreement; the amount isn’t very reasonable or fair.
Now, for a big general statement: according to my copyright/internet prof, some of the craziest software licenses you’ve ever heard of are just peachy in the eyes of the law. A provision that only one person may use the software, ever? Just fine. A provision that the software belongs to them, and you only purchased the disks it comes on? Just fine. A provision that even the disks themselves still belong to MegaCorp, and if you copy the software onto other disks, those disks become the property of MegaCorp as well? Still okay. A software license is basically a contract that you accept by performing a specific act (installing it/opening the pouch/whatever). If you don’t accept the terms (assuming the terms set are legal in the first place), you must not use the software, or you’re in the wrong.
And there are some capital-C Crazy licensing agreements out there. One that really astounded me recently involved a software package that included some adware/spyware. The licensing stated that by installing the software, the user agreed not to use any ad-blocking software (such as AdAware), and if any was discovered during installation, the program would erase it. Somehow I really doubt that a license empowering the company to remove other software that the user legally installed is acceptable.
Anyway, no doubt some actual lawyer-type will come strutting along now and correct me, so I’ll cut myself off here and say this: if this is something you’re thinking about doing on some software, you can get away with quite a lot in a license agreement, but you gotta talk to a real lawyer-person to be sure.