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First thing to do, is to forget the term "humidity." Keep a water container in the enclosure & moisten a small area of the substrate on rotation.
Brachypelma are desert species & do not need much moisture at all. But always keep a small area of the substrate lightly moist & then allow it to almost dry out before moistening another area. This stops mold from becoming an issue.
I simply move my water container within the enclosure every couple of weeks & overflow it a little.
With heat, if your home is warm enough for you, then it is warm enough for your T. So for most of us extra heating is not needed & if you do really feel the need for extra warmth, then take some time to think about what you are going to do, as it is very easy to overheat a T & dehydrate it & thus kill it. NEVER use a heat mat under an enclosure, as T's burrow to escape heat & thus get quickly killed by heat mats under an enclosure.
I have used a heat cable to provide some extra warmth around my T shelves in the past. But found even keeping that cable away from direct contact with my enclosures. It was still drying out my enclosures too quickly & thus almost certainly dehydrating my T's too.
Daytime in a desert maybe hotter than the room you keep your T in. But that does not mean your T is happy with desert heat, as in the wild they stay out of the sun for much of the day & also don't forget deserts normally get very cold at night. So is your room that cold for your T?