[lil fu fu girl]

Have you thought of the possiblitiy of a yeast infection.
If it is crusty, smelly, and itchy, and the skin has the appearance of "elephant skin", then it could possibly be a yeast infection.
You stated that he was a rescue, yeast infections are prevailent among rescues due to their compromised immune systems.
I would definitely contact the vet that you said you have a good rapport with and discuss this possibility. He might be able to suggest a plan of treatment that is not too expensive, and also give you nutritional suggestions on how to strengthen his immune system.
Poor little guy!
Best wishes........ Keep us posted on him