Good on you! You seem to know your stuff.
The only thing I feel needs to be added, is that the heat bulbs WILL be a pain for humidity unless you change the set-up a bit.
Try covering the screen top with tinfoil, Saran wrap, or a wet towel (obviously leaving a small space open for ventilation)
Or you could get a piece of plexiglass, and drill holes for ventilation.
Also, how are you measuring these temps? Honestly, a heat gun is amazing. If you're using an analog thermometer, chances are your temperatures are way off.