Best wishes to your wife and also for you. My dear sweet wife fought the good fight for 5 years before the cancer finally won the battle for her life.
My wish for you is that you find 30 minutes a couple of time a week for you to exercise and to relieve the stress of being the support for her. The feeling I remember the most is of helplessnes and everything being out of my control, being worthless and weak.
You need to keep healthy and strong for her and for yourself. Exercise in whatever from you choose will be of great benefit to you. Read everything you can find on colon cancer, knowledge is power. Remember to be her most ferocious advocate, no one else will look out for her as much as you.
Sorry if I am rambling but typing this brings back many painful memories and some good ones too.
God Bless. Be Strong.