I'll second the kudos for working through this before bringing your snake into the environment. This is the responsible way to do it. I get so frustrated with the "I brought my snake home last month & he never even plays with his duct tape ball. What do I feed this thing?" type threads.

Also, BPs seem to stress easily and feel more secure if you black out the back and sides of glass/acrylic enclosures. I used a thin black foam (from a hobby store) secured with glue to the outside of my tank. This may help a little with your temps and will definitely give a better sense of security.

It's tough to tell, but your tank looks rather tall. Not a big deal, but as BPs are not climbers, that extra height offers more air to heat.

I also lay small plexi-glass panels ($2 from Home Depot) over my screen on top of the tank. This will help keep heat & humidity in. Covering the screen in aluminum foil is also a popular option. UTHs are necessary, but do very little for ambient air temps if your room temp is too low.

I went with a 20 gallon long tank from the beginning and just ensured that I had it filled with enough clutter for a sense of security. Identical hides on the hot & cool side are good. I struggled a great deal with my temps & humidity. I have a UTH on both the hold & cool sides controlled by separate Ranco thermostats. The big box pet store type brands are way behind in the world of thermostats. My Rancos (very similar to Johnson) are actually designed for commercial HVAC applications, but work well for many of us.

Welcome to the addiction, err I mean hobby.