Poor punkin'
! It's so hard when something is clearly going on, and you can't figure it out.
My mind is kinda reeling w/ ideas, but I'm just going to post a few and then think some more.
Def check thyroid like you're thinking, just to rule it out. Have you looked at Cushing's symptoms at all? Is he peeing/drinking alot, eating too much...ie obSESSed w/ food, have a pot belly (was his wt gain unusual), lethargy...anything...? See symptms about 1/3rd down page here:
Cushings (Hyperadrenocorticism)
Also, has vet given steroid shot just to *see* what happens to the sympt afterward? Ie, does steroid stop the itching or anything? I'd be curious to see if steroid did anything bc if it did, I might be thinking allergies/seasonal. With the scooting, you may want to try having them put hydrocort cream on it, and/or diaper cream...it may help a bit w/ the comfort level and the inflamed tissues.
Was scooting this bad prior too the expression? I hope vet didn't hurt something when expressing.
How long has he been doing all of this? Any red patches on belly or discoloration in his arm pits? I'm sure vet palpated his abdomen...?
Have your Dad palpate his teeth, look at roof of his mouth, check for nasal discharge.
I know I'm all over the place...but all his sympt are so random. I so hope you'll get answers. Maybe Crystal will have some good ideas too...she'd be a good one to get on this thread.