Good news!
I was able to return the crappy Zilla temperature controller and small UTH. Just this I got in the recommended Hydrofarm heat controller, large UTH, and a 25w red light bulb for night time viewing
. Slinky is now all setup in his 40B and loving it!. I have the heat mat set for 83* and it seems to be doing a good job.
Here is his new setup and his favorite hide. (a fake flower that my wife put in just for decoration.) He loves curling up between the petals.