No, you won't lose him. Many cats go into remission and even those who don't live long, healthy lives. Someone wise once said, "Remember, he doesn't know he's diabetic. He knows you are giving him lots of extra attention, some yummy new treats and good food."
My vet wanted me to feed prescription food. Your vet is not around when you feed him, so feed him what you want. Lots of us (including me) fed low carb, home tested and just didn't bring it up at vet visits. For me, I took him in once he was in remission and she was astounded - wanted to know all about the
www.catinfo.org site and testing at home.
A blood test for $18 is very reasonable. You can just do that, compare it to your numbers at home (gotten without the stress factor) and proceed accordingly. You hold the syringe; you buy the food. You need the vet for the insulin and shots and stuff, but I wouldn't try to convince him that these weird people on the internet know what they are talking about. Just keep treating George the way you think is best and work with (around) the vet.