The problem is that of the 30-35% that don't want Hillary, they're split down the middle between the archaic conservadems who want someone like Manchin who is to the right of Hillary, and the leftists who want a Bernie Sanders. Uniting this group would be next to impossible, and even if it was united it still wouldn't be enough.
Not at all. It's all about perception. Somebody like Schweitzer (governor of a Western state+guns) or Webb (Reagan's Secretary of the Navy) could run, with the background to attract conservadems and some of the policy positions to get leftists.