Glad to read there's improvement. Has he started to crow yet? If not, you'll know he's really getting better when he does? Any thoughts as to what you'll do with him when his health returns? Quail do best in pairs...
Try meal worms. Live are best but they can be bought in a freeze-dried form. Boiled egg is good, but be sure to hard boil-very hard boiled. All egg should be well cooked. Water soluble vitamins may help.