He's probably underweight from not eating cause he was kept in such bad conditions.
From what you said it sounds like it really does have an RI, so at least tell the vet that injectable baytril would be the best choice for medication. I wouldn't even bother offering food until the RI is under control as that is the more pressing issue.
And 85 on the high side might be a little high for a blood but if the ambient temp at the cold side of his tub is lower I would probably leave it to allow him the choice, a slightly higher temp can be good for helping him get rid of the RI.