I finally found all 50 Mickeys!!!! However, I only received 750 credits and a gold pin. Is that right? I was under the impression that I should have gotten more.
No, they weren't. As pointed out above, you only used to get 150 credits and the pin, so you should be considering yourself lucky to get the 750 credits!
But I think it was worth to do the hidden mickeys a while ago even if the credits weren't very good because if you had access to a disney park, it gave you the gold set. But you can't get them anymore.