has he been scraped for demodex mange? Thats what Leo looked like when he had demodex.... patchy with red angry scaly parts. It took 9 weeks of Ivermec to get rid of it. Does he have a "mousy" smell?If not demodex than perhaps he is allergic to lamb?
My Lola is slightly allergic to lamb and my sister's dog had crazy skin problems until she eliminated lamb. Apparently, lots of dogs are allergic. Duck is supposed to be best for allergies. No amount of vitamins and fish oils worked until I started her on desensitization therapies for her other environmental allergies. Unfortunately this involved a pretty costly skin allergy test.
Also, you can try benzoyl peroxide shampoo as it is the only product that acts as a follicle flush and is one of the best antiseptic shampoos out there. DermaBenSs is the brand I use and buy from Amazon.