I finally got it together to read your excellent article, Mark--descriptions of the progress of the disease take me right back to where I was during my father's journey: witnessing, helping when I could, feeling helpless when I couldn't help.
I was very moved by your writing and honored that you chose to share it with us. For what it's worth, I'm sure my father would have read it and said something along the lines of "He's one heckuva guy."
As for me, I'll just repeat this line of yours that struck me: "In the future, I may be in a state where I can't speak or write anymore, so I want to say it now: Thank you!"
All I'll add is: Keep writing.