When you are with someone for decades, they become a part of you ...... creating what feels like a very strange new life is incredibly hard, and especially hard when old. Any change is hard when old, let alone suddenly finding that 2 is now 1; that the patterns which formed your life for 65 years have suddenly been blown out of the water. It is not just the sadness of the loss of a loved one, but the the vanishing routines - the cup of tea made in the morning and brought to you in bed, the daily walk together - all the little habits that make up a life together.
All you can do is to be there for him; staying in touch; popping round with the occasional meal; including him on an outing etc.
Does he have hearing aids? Can you make sure they have all the bells and whistles so that he might be able to connect to the radio/TV or audiobooks?
Why Are Blokes Obsessed With Noisy Gadgets??