Trumps wins need to be kept in perspective when considering who will be President rather than who will be the Republican candidate.
He polled just over 34,000 votes in Nevada. That's about 1% of the population of the state and 0.001% of the entire US population (courtesy of the BBC).
If he runs against Clinton I believe it will be a landslide for Hilary (and I have no particular leaning towards her).
Maybe. Personally I am not sure America is ready to follow the first black president with the first female one though.
Mainly because all the Americans I know regret Obama and appear to want something less middle of the road and wet.