If you have access to the meloxicam, I would give it a go. Aspirin wise, I use the low dose adult chewable kind, 81mg, ground up into something I know will get eaten (for my flock, watermelon is the slam dunk, followed by scrambled eggs) and it goes right on down. Not sure if it eases up the side effects when compared with the regular white aspirin, but I've always got some for just this purpose.
This kind of wound is going to do all manner of gross things while it heals, because it has to dispose of the flesh that died, and then regenerate to bring everything back together again. Once he starts to scab over on the neck wound, leave the scabs in place unless you have reason to believe there's a pocket of infection developing. As you've noted in other posts, keep smelling the wound site.
I'm glad to hear he seems to have escaped with his digestive abilities intact, and that you've got some antibiotics on board.