I am so sorry for what yu are going through.  We have felt your pain.  We had to put down our yorkie "Baby" who was 15 years old.  She had always been so active and enjoyed sailing with us every week-end. Her sight was going, her potty habits could no longer be controlled and at night when she sept with us we could hear a low moan when she changed positions.  It was time.  It hurt beyond words but for Baby's sake we had to let go.  I held her all the way to the vets and my husband, bless his big heart, held her, told her what a god dog she was and stroked her for several minutes after the shot and after her heart had stopped.  If we had not done the right thing for Baby we would have only been thinking of ourselves.  Baby lives on in our hearts forever but is now sleeping in peace with no pain.  God Bless you and Chewy and take solace in the fact that Chewy loves you and will be at peace with no pain.      
 