Hi Least,
Animals' love is unconditional, which I think is why we feel such emptiness when they leave. My beloved pugs passed 2 Septembers ago, weeks apart from each other. They were 13 and 15, so they lived long happy lives, but still. The grief and adjustment period was awful...we were a tribe, and I didn't really remember my life without them being there. I had never had dogs before them.
I didn't handle it very well...crying spells/panic attacks at work...Bringing the rest of their food to the local shelter felt terrible. A friend that lived closer to it offered to do it for me and I gratefully took her up on that.
I'll echo what Opivitol said, about how Jack was so cherished and cared for, and if anything hopefully you can find peace in knowing that. A friend told me, "you gave those pugs a better life than they ever could have possibly dreamed of." I'm sure you did the same for Jack. It won't make his absence any easier, but I do believe there is a certain peace in the knowledge that we gave our pups the best life possible in the time we had them.
Pls feel free to message me if you ever need an ear.