The tail bone pain has me a bit puzzled .... have you had a previous injury to your tailbone?
Quite possibly - I've fallen off enough horses - I have a difficult time sitting for long periods of time in most kinds of chairs unless I can pull one leg up and sit on it (I'm so short that my legs don't reach the ground on most chairs, so that's usually the only way I'm comfortable). Also, since this is a comfort bike, I'm sitting nearly straight up, so maybe that's part of the problem on the tail bone issue. I don't recall any specific injuries, but I only remember the big ones, LOL!