Dear Sechel,
1) You are skipping a step here, so it’s not so obvious to me that it follows that The Rebbe is Moshiach. I am not fool enough to try to debate a Chabadsker online about the exact nature of Chassidus and Kabbalah. If we meet in real life, we would have a great bull session and it would be a fun, deep, and informative.
2) I don’t know why the Kabbalistic or halachic qualifications matter. In reality, we are still in Galus as much as fifty or a hundred years ago.