Yeah they can bask too much. You want them basking for maybe 5-10 minutes at a time, any more and the basking temperature is too low.
Yeah that's fine to feed to the locust, just make sure you give them a rinse in case there's any pesticide etc left on them. I would have a go at feeding smaller locusts and adding mealworms too, see if he takes to those.
The picture is definitely undigested locust, not sure if it's from the locust but there's red-ish patches on it? Just keep an eye on him, may have scratched his insides bringing it up again.
The only other thing I can suggest is getting his faeces tested for parasites/bacteria. Parasites and some infections can cause regurgitation and if left they only get worse. If you decide to I highly recommend these guys > Veterinary Laboratory, Tests For Companion & Exotic Animals