Also as for dehydration, I have heard people soaking snakes in unflavored Pedialyte. But like mentioned, they don't soak up liquids through their skin. they need to drink and/or soak it in through their vent to an extent. The problem is even if he is drinking, if the environment is bone dry, hes going to just "sweat" the fluids out per say. I know in my house atm with it being cold, my humidity is only around 30%. no amount of drinking is going to compensate for a humidity like that on a tropical reptile.

As for heating, you need to get it to around 90F with a cool spot of 70ish. They still need heat available though at all times. It's like saying "during the day I give my boa 90F hot spot and at night it drops to 70F". That's just not gonna work. You need to provide him with a CHE at night if you plan to keep that set up you got so he can sit at be warm if wanted.

That cage is pretty nice in size but personally if it was me, I would sell it online and order a PVC cage from someone like Animal Plastics or Constrictors NW. Those cages are much easier to maintain humidity and temps with. Anyways, hope that helps some.