Den Anne Pen had a good idea, to check Major's gums. If they are pale, or if the color doesn't return quickly when you press on them, that is a danger sign!

Also, see if his nose is warm or cold. A dehydrated dog will have a fever.

I don't see why Major should have to wear the big plastic collar all the time, which is making him even more miserable. Seems like a dumb thing to prescribe for a dog as sick as he is. If you bring him in the house and stay with him, you can prevent him from bothering his sores on his backside.

If you Google for dehydration + dog you can find websites that discuss how to test Major for it. This one has a picture, showing how to test with the skin on his back:

http://www.doctordog.com/dogbook/dogdehyd.html

I agree with Den Anne Pen, that not all vets can be trusted to do what is best for your dog. A young vet checked my dog's eye with a test strip, removed it too quickly, and ripped a hole in his cornea. Required a year of trips to a specialist and hundreds of dollars worth of medicine to repair the damage.

Do whatever you have to save Major; he deserves the best care you can give him, after what has happened. It wasn't his fault.

Hoping for the best,

Dorrie