I'm almost in tears as I read this - the only thing I can say is that you must know that he loves you, and he knows that the decision you make was made in his best interests. Also, he is relying on you to make sure he's ok. You are the only one he can count on. I think that one day you will wake up, see him, and you will just know.. that's what happened with ours.

And if it's any consolation, when my cat went missing and I was so upset because there was no closure, I swear on my life I heard him purring one night at the end of the bed, and I could feel the lump over my foot where he would always lay. That night I dreamed about him. When I woke up (in tears) I knew he was ok. Our pets know. Good luck. My thoughts are with you