It's important to really space out feedings, as well as downgrading size, when you're trying to overcome a regurge issue. You need to give them time to rebuild the gut bacteria that aid in digestion and if you feed too big or too often, it can easily become a slippery slope to death. If you're fellow is so weak he's having issues simply swallowing now, you'll probably need a bit of luck if he's to pull through. You should generally skip a meal or two after a regurge before feeding a smaller prey item and then give them plenty of time to digest and see how it goes. If all's well, you can usually get back on a normal routine after a couple of feeds. Since you're now dealing with a chronic regurge issue, you'll want to slowly build back up, keeping meals small and spaced out until you're sure his digestion is able to keep up with the intake. Sounds like your vet was on the right track with downsizing prey but other than that, it doesn't seem like he was very helpful. Wait 2-3 weeks and get some nutribac(probiotic for reptiles) to include with your next feeding. If he gets it down, don't feed again until he(hopefully) poops and/or another 2-3 weeks pass. After that, I'd keep prey small and meals every 10-14 days for a while. Work on getting his digestive system back on track and then you can start rebuilding his strength by slowly increasing prey size and feeding frequency. Make sure you have a proper temperature gradient to aid in digestion.