My cat Jarvis has: Eosinophilic Granuloma Complex

[Jarvis1]

Hi, everyone. First post.

Last Fall I trapped and rescued Jarvis, an FIV cat (otherwise robust), now aged 18 months. He is an indoor cat and currently isolated (from our 3 others) in a large airy room with windows.

PROBLEM
He has a raw, and sometimes bloody lesion that he scratches under his chin/neck with his uncut back claws. This grew over time. He scratches violently at it with his hind paws and cries with pain—sending blood flecking outward on the floor and walls. He re-opens the wound each time it seems to be healing (every few days). The cause is unknown, perhaps stress or allergy.

Vet Diagnosis (2 days ago)
Their working diagnosis is Eosinophilic granuloma complex. Jarvis has always been extremely fearful and basically cannot be handled (sometimes, we can pet him while he eats, or my wife used to be able to stroke him as he seemed enthused by her; no more). I had to trap him to get him to the vet. He wants to be with our other cats but they dislike him, and harass him, except one who tolerates him (thus, socialization--our original challenge-- has been frustrating and we even tried a behaviorist but got sidetracked by this EGC issue).

What has been done and reviewed by vet:
• He is in an E-collar (will be for 3 weeks to permit healing of lesion).
• He is receiving antibiotics mixed in his food. (He completed a short course of Prednisone).
• I changed his food from Natural Balance Chicken/Turkey (which my others eat) to MERRICK BG (Before Grain) BEEF
• I switched to steel food dishes vice flat poreclain.

2 days off sedation he eats but I need to steer the food to him. The collar is a distraction and he is now a bit listless, sleeping a lot. I'm told this is normal.

I looked at some of the older related posts on this, though none seemed to have his location issue. Jarvis is a beautiful animal with a great spirt that has been utterly reduced by this (in addition to the socialization issues). Any advice you can share is appreciated.

Thanks.