Emma, I am sorry that you have this to consider. (one of the many things in "the manual of life" that they forgot to give us at birth).
As his cancer advances, fistulas (openings) can develop which is natures way of getting the bad stuff to the outside of the body. These can drain and sometimes the matter that drains will have an odor. You should mention anything unusual to his doctor just to be sure. As far as bleeding goes, yes this could happen if the cancer invades one of the many major blood vessels in the neck. I don't know if a doctor can really tell if this is going to happen in a specific patient. The tumor growth might also cause breathing difficulties which can be relieved by a Tracheostomy.
I can't think of anything that makes this easier for you except the age old "take one day at a time" and in this case maybe one moment at a time. I would also offer that pain control should be something your doctors are very keen on.

Take time for yourself too....