I'm also eyeing the 24 TS-E which I'm hoping will help to control perspective additionally. I will deffinatly have to work on the ambient lighting as well. What is the best way to control light sources? Should I have them dimmed extensively and use a longer shutter to compensate?
No need to buy more equipment. I would rather look into ptgui or hugin (aka panorama tools). both have outstanding side effects/functions to compensate lens distortions and perspective control, much more granular than what you can achieve in photoshop, even if you are not using them for panoramas. it's quite simple to shoot 2-3 overlapping wideangles, and then stitch them together and then worry about cropping.
As for the light temperature, you want to be as far away from the deep red as possible. so crank up all the lights you have... you'll probably end up with 3000-3500k color temp. ignore the light from the window (>5000k) and maybe fix it later in photoshop. make the different color temperatures a virtue, rather than fight them...
For processing, these were exposure blends with Photomatix, but I'm left with the dark halos. I will try to go back to the original files and see if I can drop in some more neutral ceilings.
did you use exposure blending or HDR? i am confused. if exposure blending still gives you that amount of halos, play with the "amount" (aka radius) slider, maybe bring it down to -3 (it looks like +10 right now), or drop one of your exposures, in other words make your blend only from 2 instead of 3 exposures.
keep us posted how it goes.