In regard to the song on the radio giving you comfort, I don't know what that actually is, it could just be your mind accepting the reality, that you are coming to terms with the fact that he is gone, or is it a gift from the other side saying all is well. Personally I choose to believe the latter, and he is telling you he is in a far better place now.
Reading your story, broke my heart. I recently separated with someone who I fear is so very close to liver failure, kidney failure, a stroke, or some other life threatening ailment. Makes me realize what a priceless gift life truly is. Take care of You