I hope Mac will be fine for a long time, yet. I see you got him some medicine, but I would be very careful giving him something your vet hasn't approved of. When Fister was sick, I suggested to the vet to give him vitamin B, but he strongly discouraged it, I can't remember exactly why, but he said it could make matters worse. The other vet agreed. Perhaps you could ring and find out.

Do you feed him a diet to prevent kidney problems?
Sending lots of positive thoughts to your sweet Mac.