When committing the vow of marriage the part most people pay title attention to is the "worse" part of "for beter or for worse. Nothing reveals true character more than "worse".
I am truly blessed to have an understanding wife.
Pray
Read Bible
READ OVER AND OVER AND OVER FIRST CORINTHIANS 13.
Read it daily until you can almost say it by heart.
Pray
Read specific scriptures about marrage.
Find and attend regularly a true Bible believing church.

PRACTICE
What it says in 1 Cor 13

Vern, kudos to you for being proactive and getting your end of life book assembled! It will allay many fears that your wife might have about the future when you pass away. You can also sit down, once the book is somewhat completed, and visit with your wife, and then your four daughters regarding your end of life book. This book will be such a tribute to your wife and daughters as you honor them with this preparation. Vern, again, kudos to you!

Jim, thanks for your comments on an 'end of life' book. Regardless of when I die I need to and will start the same. Otherwise, what a mess for my four daughters to plow through.

Judi, about six or seven years ago I created an End of Life book for my wife. The contents include sections on Finance, banks, a, complete list of all the people to call when I passed away, our cremation receipt that we purchased years ago and insurance policies. Judi, this book is profoundly helpful to my wife, Sharon. We go over it about every six months to update the book regarding credit card numbers,, insurance papers, car titles, etc. etc. My wife, Sharon feels this to be so reassuring for her. There are books through eBay or Amazon that have created end of life books you simply fill in the blanks. Just a suggestion. Jim Jones

Lots of good responses above. You might consider sitting down with your husband and explain that for you to provide the care he needs, you need to take care of your self. Perhaps a few half-hour rest periods for you scattered throughout the day.