Ok good to know you would like to save him, have him in warm housing, and great that his feet may still have circulation. Housing him in above-freezing temperatures for the next several weeks is the very best step you can take to prevent further frostbite injury while his body works to heal itself. Other things you can do to give him the best possible outcome include 1) Keep his feet as clean and dry as possible to help prevent infection. No need to wash his feet unless he is getting poop on them, although warm Epsom salt soaks will soothe pain and will help deter any chance of infection. 2) A baby aspirin given once daily or 1/2 baby aspirin given twice daily will help with pain, which will improve his appetite. His appetite may remain poor for the next 2 weeks or so until pain diminishes. 3) Topical triple antibiotic ointment, vetericyn spray or other topical antibiotic/antimicrobial will help deter infection, especially if you see any open wounds. (For example if a blister accidently breaks)
If you were able to tell what color his blisters are, that would be a huge clue as far as his prognosis. But I understand that his willow shank color makes it very difficult to tell. If there is only clear fluid in the blisters, his frostbite damage is 2nd degree, meaning that the damage only penetrates skin-deep and he should heal with no lasting damage. If blisters are red, that means at minimum 3rd degree frostbite, which penetrates into tissues and causes permanent damage. One way or another, in 2-3 weeks you should have a much better idea. I hope he keeps his feet and is able to contribute to your son's breeding goals.
