Yes, you certainly can dry them for future use. As to how many... I've never seen a dosage for rabbits, but since they are a very nutritious feed, I just give mine whatever I have until they run out.
Mine will eat the pumpkin flesh and skin as well, but they prefer it cooked. They prefer the Small Sugar Pumpkins to others I've had. They are a heritage variety and I save a handful of seeds for planting the next year.
Squash seeds work as a dewormer as well.