As for why Nick was being discounted by the others, I believe that mostly stems from the fact that he was not a part of the Bachelor clique that most of these people belong to. They party together, go to reunions, hook up, etc. Clearly many of them know each other and hence their very clear...and nasty...disdain for anyone who did not belong to their little group. This is why they felt the need to treat the fans as being "undeserving" and were able to dismiss that poor virgin guy (whose name I unfortunately forget), so easily last night and during the show.
Rachel did in fact bash him and treat him poorly so that is not a fantasy or a figment of his imagination. He does not seem to be wollowing in that in any way, but made a rational decision to keep the money based on her behaviour. That is a natural consequence. Why does he need to be more supportive of her? He seemed to listen to her crying and going on endlessly about Michael and wanting to quit. How much more supportive does he need to be? He said that if she had been more supportive, he would have shared. She wasn't and he didn't. It sucks, but that is life. Live and learn ... all around.