Thanks for keeping up to the minute on Terry's condition. I'm really glad you got medical advice about him. Yeah it sounds like you have some intensive care to give him and it seems like you're up to it. From your pictures and your description I suspected that he might have swallowed more of the substrate than you were able to get out of his mouth. Regarding the temperature, I have to keep my Grays tank above 60 degrees or they start to exhibit behaviors leading into their winter dessication period. About the idea of separating them, if the Vet didn't tell you that you should do that you might consider leaving them in the 10gal. for this winter since they won't be as active as in the other seasons even with the heat and it'll be much easier to keep good heat in the smaller tank.
Please keep updating this thread with Terry's progress, I really want to read about him pulling through this.