I am very sorry you have to go through this. Preparing for your husbands death has to be horrible.
If the doctors have said there is nothing left to do then keeping your husband as comfortable as possible is what you want to do.

Have you contacted Hospice? They are a wonderful organization with some of the best nurses you will ever find. Your husband couls stay home and when his time comes--go in the comfort of his own home.

Get his docs to order Hospice if they havnt already--they are also there for you.
As far as the actual process of death--he will most likely slip into a coma as his vital organs shut down.

But dont let that stop you from talking to him as his hearing will still be working.
Play calming music in his room, pray with him or whatever else you know he likes.

As long as he still has hope--there is nothng wrong with that but dont be afraid to talk together if you think he will--that is where Hospice can be a big help.
You have to take care of yourself and can not be expected to do all his personal cares--so I hope you will quickly look into hospice care.

My prayers are with you.
Bubbi