Hey man, sorry for your many losses. Seems like you're keeping your chin up though - good on ya.
For short sweet practicality in a response - what I have done in my first and/or second purpose-built herp rooms, and/or intend to do on my upcoming third one.
- Locate the hobby room on the lowest floor so you're not fighting air temps as much.
- Make the narrowest dimension no bigger than 12'0".
- Floor drain, utility sink if you have the space.
- Frame the room's walls with pressure-treated 2x4s. Bottom and top plates too.
- Insulate the walls and ceiling with mineral wool board or batting.
- Sheath the walls and ceiling like you would a shower - cement board or at least a paperless drywall, with a roll-on moisture membrane (Redgard or whatever) over that. Those elastomeric coatings accept latex paint just fine - it'll look normal but undercover it'll be tropical high-functioning.
- Floor the room with a single piece of roll product. "Vinyl sheet flooring" is the search term. They make some nice looking stuff nowadays, that's tough as nails and also won't break the bank.
- PVC composite (or other inorganic) baseboard and door trim.
- Put a ductless mini split in the room. Don't hook the room up to the common HVAC.
- Overbuild the electrical. Standalone circuit, for one thing. DON'T make it weird by failing to install the standard duplex (maybe make em quad though) outlets every 4 feet at normal height along the walls. BUT, ALSO put in a junction box (so it's easy to remove) and run surface-mount outlets (also so it's easy to remove) in an upper course, 4 or 5 feet off the ground.
- Definitely put a dimmer switch on the overhead light.
- Exterior-grade door & threshold to the room (fire coded) with a deadbolt. No lock on the knob, just the deadbolt.
- Small bench / countertop area with same length of cabinets above if you have the space.
- Solatubes yes if it's a 1-story. Skylights no. Too hot, and prone to leaking eventually. Nice idea that fails upon contact with reality.
There's some thoughts. Good luck with the insurance company, the building & permitting department(s), and your contractor(s). Hang in there, man.