You might want to consider putting the heat lamp on a dimmer. The lamp on a dimmer is very helpful as they do put out a lot of humidity zapping heat. I maintain a 90 hotspot, 82 ambient and 55% humidity with my set up. <it wasn't easy and I considered a new career as an alcoholic during this time of my young Bp's startup.>

Might I also suggest you do the foil/ tape trick on your screen lid? Will help hold in both heat and humidity.

Here is an example of the foil/tape thing.