How long had you been in the room when you noticed the mold?

If not long, than 3500 points + a move was quite fine (IMO)

If for a while (multiple nights), I'd probably want 1 night's worth of points (so I think 10,000 at that hotel).

That said, I wouldn't waste time fighting for more than you got. First, life is too short. Second, you've already accepted (it seems) the hotel's offer. The time to seek more was when you were talking to a manager.