I can answer 1, 2, and 4.

If you do a RC (or series of them) and fail, there's no problem with saying to yourself "ok, so I'm not dreaming now. Nice to know". But after you see that you're in reality, stop and take a second to look around, observe your surroundings, and think to yourself: "If I were in a dream right now, what would/could be different?" It helps raise your awareness in general.

The general wisdom is to do more than one reality check at a time, just in case one of them gives you a false negative. Personally I do the nose plug test, reading test (alternatively I try to use powers if nothing is there to read), and memory test (what was I doing an hour ago?).

As for when it's going to happen? Depends on the individual. Some people get theirs the first night they learn about it, others can take months or more, although it's usually not that bad. I got mine after the first week or so. Just keep improving your dream recall, since it's totally possible you had one, and just didn't remember it.