I'm sorry to hear you're still having trouble with Binky. I had hoped that the flea treatment might work, it was worth a try. I went over your food list, and looked quite good some of them I use myself. The freeze-dried I haven't used but looks really interesting. It's not readily available in this area. Have you tried the coconut oil? I think if it was me I would be rubbing some into the affected area where Binky is doing a lot of licking. The organic virgin coconut oil is a quality food product, and shows no sign of side effects. I myself use it internally and topically for dry skin problems and it works very well. The thing is too, if it doesn't work at least you can use it around the kitchen for cooking or eating, and it does make a good hand rub.
I have a video from Cornell University on how to give your cat a pill or capsule which might be of help to you. I also have some threads on pets.ca for you to have a look at in regards to the Benadryl administering.
Is the Benadryl you got from your vet a hard tablet? If so take a sharp knife and cut it in half, and apply butter to it. Not too much you'll want the tablet to be able to slip off your fingers very easily and down the cat's throat. Follow the instructions on the video.
I can really sympathize with you when it comes to dealing with this rolling skin syndrome having gone through it with Yogi. You feel so helpless when you see the poor animal going to the stress of the symptoms and of not knowing how to cope with it, let alone not knowing yourself what to do. I think if I were you, and you are not comfortable with your vet I would be asking around to see if someone could recommend a vet that is willing to listen rather than dictate. Money is too hard to come by just to blow it out willy-nilly without getting decent results for your dollar spent.
If you would like to PM me, I have the name of a vet who is down in the Toronto area who might be of value to you - or at least worth looking into.