Poor guy! I would try tapping his nose with the food on a blunt tweezers a bit, even alive and wiggling a little. Usually that will trigger a bite instinct. If that doesn't, force feeding is about all you can do right now. You may want to try hydrating him with a pedialyte/water mixture. Use a multivitamin dust and also a Calcium dust (I use calcium 3-4 days a week and multivitamin 1-2 days a week). I would say that pieces of night crawlers are the best thing you could give him right now. They are soft, digestible, and high in nutrients. If you want to fatten him up a bit, you could use wax worms but those are pretty deplete of nutrients so it really isn't the best. There is a possibility that he has a disease causing the issues, so make sure you keep him and his equipment separate from everything else.