In one post you mentioned that he didn't seem to be "there"
I know exactly what you mean.

When Toby (my/my parent's dog) had gotten sick this past June I went to visit her and she wouldn't even look at me. She'd look away no mater how you tried to get her attention.
I made the decision to send her to the bridge the next day.
That night my parent's couldn't even coax her into the house.
We knew she had lived a long life and was now tired and was ready for her trip to the bridge. She was no longer the happy girl she always used to be, and I knew it wasn't fair to her to let her go on like that.

The next morning we spoiled her rotten, we fed her treats and 1/2 a jar of peanut butter.
I made the appointment for the vet to come to the house, and as soon as he pulled in the driveway she walked for the first time that day, and laid under her favorite pine tree... and that's where she ended her life on earth and started her new life at the bridge.

Her message to me was crystal clear that she was ready.
I think Thunder's message is clear as well.
{{{{HUGS}}}} to you.
And {{{HUGS}}} and special treats to Thunder.
I know you'll make his last few days on earth very, very special and he will be grateful for it.