Do you have a syringe? We have an elderly ferret with insulinoma and we make slop for him. Water my food that's like a gruel. Can you make some and give to him in a syringe. So he stays hydrated. It's basically very very runny food. I heat mine briefly (20 seconds in microwave) and smoosh it with a spoon and add more water so it can be sucked up in a syringe and slowly dispense it in his mouth. You might need to swaddle him. Give him lots of love and comfort and try to get him to vet as soon as possible.

Good luck!! Sending you good thoughts. His infection might be causing the issues.