That's good the teacher is giving the rabbits to new homes. I just really hope, for the rabbit's sake, that he's giving them to people who are going to take them to the vet to get their various issues addressed.
The House Rabbit Society, www.rabbit.org
, is the site I most often recommend for owners who want to do more research.
Um I can't tell you how much the vet will cost but keep in mind that rabbit vets usually are more expensive then regular cat/dog vets. If he really does need his leg to be amputated and all that then I'd guess it'd probably get pretty expensive. It sounds like he has a lot going on too, so the cost will go up depending on how many treatments he needs. See if your vet will take care of his leg and neuter him at the same time, then at least you only have to pay for anesthesia once.
His cage sounds smallish to me. Or at least the length does. Maybe you can get him a pen to play in and attach it to the cage? With all his medical issues and being in a new home I don't know how active he'll be, but once he gets more settled in and heals up don't forget to give him plenty of exercise time outside of his cage.
Hay is the most important part of a rabbit's diet, not pellets. He should be provided with a constant supply of clean grass hay. Most rabbit owners use timothy hay. I don't know about those foods - pellets should be plain and healthy and not include things like berrys and nuts and colored pieces. He doesn't need the salt or mineral blocks. Pine, unless it's kiln dried pine, is also not a safe type of litter.
If you're going to keep him outside I suggest getting him a nice durable outdoor hutch. Those wire and plastic cages are really designed more for keeping them indoors. Heat stroke is a real risk for rabbits, especially if they don't have a shaded or boxed area to go in to get out of the sun during the day.
I wouldn't give him vitamins - just a healthy high quality food and that should help his fur. His eyes sound like a medical condition that will have to be looked at by a vet, same with the dandruff. Dandruff looking flakes in rabbits is usually caused by mites.
For litter box training - You should probably remove the bedding from the cage and only use it in the litter box. Also put hay in his litter box or hang hay in a hay holder right above his box.
I can answer other questions if you have anything specific but I really recommend that you check out the House Rabbit Society website to learn more
Good luck! Keep us updated on him! I'd love to see some pictures of him if you have any.