I lost my 21 year old brother in law to leukemia a few years back. Even though I didn't experience the same severity of pain as my wife or in-laws, I was still there through all of it. I saw my parents-in-law taking care of their dying son, who only a few months ago was a promising ornithology student, and the fittest player on his soccer team. What you wrote resonates a lot with what they said, and what I saw them go through.
Thank you for including the reference to Daniel 3, it has been a source of strength for my in-laws too. My brother-in-law got a lot of his strength from Philippians 1:21 "For to me to live is Christ, and to die is gain."
The love and care that you provide to your son does not go unnoticed or unseen.
One thing I learned from my in-laws' tragedy, was that the grief never goes away, but you will grow stronger in dealing with it.
I will be hugging my own kids extra-hard when I get home from work this afternoon.