Probably not as tough a climb as one would think. American voters are sick of supporting people for both sides of the equation who later on let them down after numerous promises to the contrary. Trump offers a fresh view os things. Many are ready for just such a change.
Depends on the person. Some have a deep-rooted distrust based on hearing and seeing quite a bit of information (and we all know that the information we use to process reality is half-true at best); others don't have any prejudice (not saying prejudice is a bad thing) and will naturally be easier to bring on board.
I agree with you, his appeal is unlike that of a politician. Even some Bernie supporters have Trump (not Hillary) as their second choice.