Hello,
Poor thing! As AHBD said, it could be multiple issues. Adenovirus is a possibility, but, so is
calcium & UVB deficiencies also.
Definitely post a picture of the tub you will use for outdoors for him to get some sun. At 53
with sun in a darker tub, & a basking light that would probably be pretty good for him.
Are you getting fluids into him also & what type of calcium are you using?
Let us know how he is doing.
Tracie