Hi Kerry -
You are certainly getting a lot of advice here - that should tell you that as a patient or a caregiver, a few of us have been there. It seems that no one prepares you for the worse part of the treatment ... after the treatments stop. Think of it this way, his body is having to replace all the skin inside his throat --- repair damage to the outside (surgery &/or radiation) and this takes a lot of energy. The month of recovery for a week of radiation is about right - I've also heard (and believe) it takes 1 week of 'recovery' for every 1 day in bed.
Here's a couple of ideas: 1) consider depression a serious fact for many going through this hell. In fact, I nearly lost Ken to depression instead of the cancer. Hall his butt to the doctor (your family doctor) and talk about anti-depressants.
2) caloric intake -- Ken was switch to a Jevity with more calories which seemed to help with the energy level (remember the body is working over time to repair the damage from treatments & it needs energy)
3) Physical Therapy -- Worked wonders for Ken. At around 4 1/2 - 5 months and still not getting around very easily, Kens doc prescribed physical therapy for 4 weeks. Insurance covered the cost. The PT helped in so many ways -- A) helped range of motion & strength B) got him out of bed & into the shower C) gave him a place to go (a purpose) and D) improved his spirits by seeing positive progress with the exercises.

Keep us posted! And hang in there.
Carol