James,
I know the pain you're feeling and wish I had magic words for you.
You have lost a dear family member and there will be a hole in your heart, as well as some of your other fur babies hearts, for a while. It will heal; give it time. Take joy from the antics and love from the others; they give freely.
Please also know that putting an ill pet at peace is a humane and loving act. I think most of the people on this site have had to face it. My girl Jamara, who was 18, we had to send to Rainbow Bridge six years ago. She was very ill, had reached the stage where we couldn't even hand feed her any more, and she was still a trouper. We love her and miss her every day, but take joy in my baby girl Pinot; it wouldn't be fair to her if I didn't.
All of our hearts and prayers are with you in this time. Remember; you and Bootsy will be reunited and he'll be very happy to see you!