I am one of those with a stage III/IV tumor that had no other mets or lymph node involvement.
With a stage III tongue cancer, if it were me, I would strongly consider radiation. Tongue cancer can very aggressive, more so than tonsil cancer. It's far better to get it all now. Have you actually spoken with a radiation oncologist? I take it that he didn't have chemo either? Multi-modality treatment is usually the route they take - see
http://www.nccn.org/professionals/physician_gls/PDF/head-and-neck.pdf page MS-11
Antibiotics can cause a thrush bloom so be on the lookout for that as well.
Sleeping a lot is a good thing. It allows the body the time to heal. If it continues for an extended time it can also signal depression.