I'm so sorry. I too have had to make this decision.It is the hardest decision to have to make.Looking back I now realize that it was more for me I could not let go even though it was time. I knew in my head it was time but my heart said no! From what you are describing its time
for you to muster up the strength and love to let go. Being able to let Nathan pass over the rainbow bridge is your final act of love for him. Hugs for you.