What is the proper weight for my hedgehog? I am worried that he's too fat.

As long as he can ball up completely, and tuck everything in, his weight is fine. Hedgehogs vary in size and build, so there is no standard weight that is right for every one. Be sure to have an 11"-15" solid surface wheel in his cage so he can get plenty of exercise. Hedgehogs have been known to run up to 13 miles per night.