i will try to answer all of your questions. sorry if i miss some:
no i have a thermostat, as well as thermometers. i have an uth that is plugged into a thermostat (just in case) as well as a reptifogger on a hydrostat (i had a LOT of issues with humidity, this is the only thing that has helped regulate it). i have a digital thermometer that i only use as a back up to make sure my thermostat is working correctly. i also have a lamp with a red lightbulb in it that is on a 12 hour timer and a second thermometer under that.
i have a cage carpet type thing that is spot cleaned as needed, but thoroughly cleaned every week (typically right after he poops)
he is about 10 months old (not 100% sure but this was the vets guess). ive had him for a few months and he has been perfectly fine before this week. nothing that i know of has changed in the last 3 weeks at least except i gave him bigger food. i might try rat pups though.