Dave, wow... I did not know your wife was suffering in that way. As I read your post, I had to wipe my eyes..... man what a beautiful way of saying what you said.....
Just as you are there for them, so too, they are there for you. No one is ever prepared for the death of a spouse or any other close family member..... but it happens..... and it sounds to me like you will be OK.... maybe not today or tomorrow, but one day, somewhere up ahead, you will realize, everything's OK.... You have a strong family for support.
Comfort to you and your family through this time of shadow..... the sun will shine again.