We just received our first ball, a 3034g normal female. We have her in an acrylic 45 x 18 x 18 in tank (~60gal) with a solid lid (many air holes throughout). We live in Seattle which normally has high relative humidity and low temps. We heat our house to between 65-70F. The tank is outfitted with two large Fluker's UTH's running at 87-92F on a Hydrofarm On/Off and a 100watt ceramic bulb over a mesh-covered hole in the the lid over the hot spot. Here's the problem/running temps:

Cold Side: Ambient = 72F
Warm Side: Ambient = 75F, Tank Floor = 91F
Humidity: 50%

I am pretty concerned about the ambient temps and need some advice on raising them. I've brainstormed (1) Higher Watt ceramic, (2) Insulating foam panel on back walls, (3) Second ceramic bulb (really hate the red ones), (4) Heat tape.

Any thoughts or other ideas?