I can always count on you to throw the fast ball right down the middle. So here we go...
Your 3 elements are on point. I have my doubts about Caleb returning to the Montana pack, but stranger things have happened in my stories. Vann's future is more flexible. Kids his age are uprooted all the time. But there has to be a good reason. Caleb just saying 'sorry isn't going to cut it.
Ah ... elephants. I still haven't decided which circus they're going to be part of.
Asa just found out about the pups when Caleb told him his history. Giles wouldn't have any reason to disclose it to the pack farrier. Don't forget.. Asa deliberately keeps himself separate from the supernatural world. Even if he heard about a disappearance (like on the podcast) he wouldn't have any reason to associate it with shifters and pups being hybrids.
The extent of his healing ability and the effects on him are still a big unknown. You know I'm gonna leave you hanging.
If/when it's time for the pups to be cured, I'm sure they'll figure out some way to decide who goes when.