#1 and MOST importantly, you absolutely need a thermostat to regulate the UTH. They are known for overheating, which can cause burns & neurological issues in your snake. There's no leeway with this. Get one ASAP & if you can't, turn the mat off until you can. If you're worried about him being cold, put a space heater in the room and keep it at about 85*.
#2) 35% humidity seems a bit low. I'd bump it up to about 50-55% and definitely get a decent gauge to measure it.
#3) Rats are far more nutritional for them than mice. Unless you've been through the ringer & have concluded that he/she won't eat rats, I'd suggest trying to switch over to frozen-thawed rats. Why are you only feeding every 12 days? Do you have a digital gram-scale that you can put him on to get his weight? Normal schedule should be about every 5 days for babies and then every 7 days once they've reached about 500g. This is my way anyway. Are you thawing the rats out in hot hot water? I take the rats out of the freezer a few hours before I plan to feed them. I leave them in their bags on the counter until I know that they're completely thawed & floppy. When I'm ready to feed them all, I'll put all the bags in a container of hot tap water (not boiling, you don't want to cook the rat) & let it sit for about 10 mins. I'll drain the water & repeat again for about 5 minutes before actually offering the rats to my snakes. I like my meals hot, why wouldn't a snake?!![]()