HI,
Chemo can cause a lot of sicknes, and also sounds like your Dad has chronic fatique, call his oncologist as soon as you can and explain to them the situation. For fatique he can get a B12 shot which will do him good and also get him some B complex vits .... will help him.. his oncologist can prescribe medication for sickness...
Always be proactive .... and keep going ..
Best Wishes Rob and Barb