No. Not 'popular' at all, in that sense. However, he is a cultural legend and was an absolute titan of a man; a very enigmatic and clever figure. Definitely one to research if you haven't before.
No, but he should be. He is the first link in world championship boxing, that most people overlook. He was the first lineal world heavyweight champion!
Really important in terms of training boxers too. Though I think there were quite a few who have more historical significance.