Heather, when you or any client refuses to follow any professional's advice, they would be irresponsible and total idiots to continue to be listed as your doctor/vet/pharmacists/ dentists, whatever. Period. It is very telling that no vet will treat him if he is in your care. It says you have blown off all of their advice or gained such a reputation they won't risk it. You have managed to put the dog into an unsafe position of having no veterinarian. It doesn't matter if you are right about the meds if you lose the dog and he is euthanized. You are old enough to know it is necessary to convince a professional of your view. My vets have always met me at least halfway even when they disagreed because I went to them with solid research and specialists in the field willing to discuss the case with them. Add to this, BRAT owns the dog, not you. The vets have to answer to the legal owners.
You locked in on sawdust and one brand. They said you could find an equitable brand. There is no research or medical proof that a dog needs freshly cooked meat.
Your posts can still be seen by the moderators, and the police can demand copies if this issue escalates to a legal challenge.
You have yourself and the dog backed into a corner. Adopt him, or offer to hold him while they euthanize him if you are really sure that is their intent. That they are pushing for intervention is a clear sign that you are about to lose any options. The police and animal control can appear at your door and simply take the dog. If you care about this dog, you need to be sure what you need to do to save him. You are not going to find that through venting on this board.