You use almost as much electricity on one enclosure as I do to heat and light six!
Keep it simple. You're using high wattage bulbs and keeping them far away when it's much easier and efficient to use low wattage bulbs and keep them close. Trust me, there's probably less chance of harming a reptile that way. My enclosure that I keep my female russians in is heated by a 40 watt sylvania light bulb in a clip lamp, and it's on a dimmer that's turned about half way down. I could literally hold that bulb in my hand all day long without getting burned. it's suspended about 6-7, maybe 8" from the floor of the enclosure. Keep in mind though, this isn't a tortoise table, this is an enclosure, with sides, bottom, top, etc. It works fantasic having it closed up though. The cage holds humidity and heat so well, and the tortoises are thriving. It's going to be tougher to keep temps high in an open-top cage though.
I hate aquariums for that reason though. I have my male russian in an aquarium with a screen top, and even with the screen almost completely covered with foil, it doesn't hold heat, it doesn't hold an humidity, it's a pain in the butt. I have to add water to the soil daily just to keep it from getting dusty.
That might actually be the problem you're struggling with. No matter how much water you dump into your substrate, it's just going to evaporate. How do you expect your tortoise to stay hydrated? In the wild tortoises spend a majority of their time deep in humid burrows, or hiding in moist leaf litter (the tropical species).
So as a start, try adding some more humid hiding spots, which can be as simple as a small container that has a hole cut in the side, filled with moistened substrate. Also try experimenting with different heating options, because currently you're heating the air in the room the tank is in, and any of the heat that happens to come down to the tortoise is just run-off.
I understand most of the information I've given you is contrary to what most people will tell you, and that's the beautiful thing about the internet. You can take it or leave it, and feel free to comment on it. This is just some advice I thought might be helpful.