Hi and welcome. I'll make some suggestions based off of what you listed.

Sterlite box: This ones lid is a bit more rigid plus it has latches. (WalMart should have them)

Sterlite 1755

Gauge: The one you listed is usual very inaccurate

Acurite

Water conditioner (No need for it)

Paper would be better over the carpet. With the carpet you won't easily see when it's wet so it can get moldy

Thermostat:

Hydrofarm

Also keep in mind with the tub set up you will need a way to keep the cool side temperatures up a bit also.