What percentage of rabbis would you say practice Kabbalism, the system of Jewish magic?

there is not really any "practice" of kabbalah. Kabbalah is designed to be a deeper level of study of jewish texts to help the individual refine his own holiness and unlock deep mysteries in his understanding of himself and to some fractional degree, of the divine. that some talmudic sages used that heightened level of spirituality to effect actions in this world came from years of study and something more than just reading books -- but living lives. nowadays, the true kabbalah has been replaced by a generic "mysticism" which people think has some sort of separate identity from judaism as a whole. it doesn't -- it is simply a higher level of the same study that we all do in judaism. there are kabbalistic texts, but studying them is a complementary action to the study of the rest of judaism.