With his coughing......it must be painful. I had to put my poodle years ago to sleep, and it is awful.....but, like you said before, making your Yorkie suffer, even though you love him so much........is only your decision.
Like that poem that says......"if you love him let him go, and he will come back to you evey day with all of his "healthy" memories....right now all you see is the pain.........
Bless your heart.....and his too......
