If the snake is so far gone that it can't eat solid food it needs to be hospitalized or the vet needs to show you how to tube-feed IMO. If the vet didn't recommend tube-feeding or something like that, try whole prey that's maybe on the small end of what a snake that size should be eating (and adhere strictly to the no handling guideline!). Basically what Deborah already suggested.
If the snake is really in the condition your posts make it sound like, you may have to go through your options quickly though. Normally people have months to try various feeding techniques before resorting to something they don't really want to try (like live-feeding) but it doesn't sound like you've got that luxury.
Regardless, I appreciate that you're doing what you can to try and help this guy out.