It looks as though you may have a FTT (failure to thrive) situation. I've had a few, and have learned that the vet bills rise and we end up paying a lot more to help the snake hopefully get well than we may have invested when we first purchased the animal. It might be best to put him down. He is suffering for sure and does not have a good quality of life at this time. However, I can understand you wanting to keep it and help it get well. I once paid a vet 600 dollars to help me with an egg-bound grayband for which I only paid 150. It never got better and eventually died of an infection.