I had the same "unexplained tiredness" problem when I was on adjuvant Xelox therapy but I didn't manage it very well and I suffered the consequences. Basically, I thought that the longer I slept during the day the faster my body would recover from the other side effects, but I think I was totally wrong. I developed severe dehydration, then kidney stones and a bladder stone and had to delay my next Xelox cycle until these problems resolved. I also missed a number of my meals and medication sessions and lost 20kg in just a few weeks. I also slept right through the filling up of my stoma bag several times, and it therefore burst while I was asleep, causing big messes in the bed.
Your DH is so lucky to have you there to help. You can help him right now by (1) making sure that he eats at least something twice a day and then takes his Xeloda pills 30 minutes after the morning and evening meals; (2) making sure that he drinks at least 8 glasses of electrolyte liquids (e.g., Gatorade, or
Oral Rehydration Salts, etc.) each day. (Note: Drinking pure water doesn't help much if he is having severe diarrhea at the same time; the consumed liquids must already have electrolytes in them), (3) monitoring his colostomy bag activity for onset of severe diarrhea (DH may need to keep a log of the amount and type of output per day.); (4) making sure that he washes his mouth very well with good mouth wash each time he has a vomiting session, so as to avoid getting more mouth sores; (5) clipping his toenails short and filing them smooth so that he doesn't snag his toenails on the bedding when the Hand Foot Syndrome and the peripheral neuropathy set in at the same time.
As for what to eat, I don't know what to suggest, but I can give you a list of what I ate in order to regain some of my lost weight. (Note: be sure to check with doctor before trying any of these): Ripe avocados, macaroni with tuna and cheese, peanut butter, protein bars, ginger snaps, bananas, cooked oatmeal, canned sardines, canned mackerel, blueberry yoghurt smoothies.
As for suggestions for what to do next, you might want to discuss with the oncologist the possibility of reducing the doses of oxaliplatin and/or Xeloda. Right now DH is on 3 pills twice a day, which is 75% normal dose for adjuvant therapy Xelox for his body weight. You could ask if he could drop down to 2 pills twice a day, which would be 50% normal dose and which is the lowest Xeloda dose thought to be clinically effective.