3 weeks enough?
Island Hopper:
I'm not sure what to tell you. Sure you can do a CPL in 3 weeks' time. In fact, just before I went there, there was one (or two?) guy there who did his/their CPL in 3 weeks. That said, I myself would definitely plan to spend 4 weeks for the course, simply because things can go wrong. The weather can turn bad, or the a/c might go tech. Or, God forbid, the course might prove to be more difficult than anticipated. Or, even worse, you might not get a first-time pass.
Sorry, but I have no first-hand experience with IFTA, so can't help you there.
HTH,
Mike