Hi,
I think I can help a bit. My kings would grow to full adult size in 3-4 years.

As for the feeding, it is common for them to rest after eating and that's best. If they get handled too much or spooked, they could regurgitate the mouse. Especially young ones who don't know better. They know what's best for them and it's fine. Keep an eye on them for when it's time to shed. They shed more often when they are young and growing.

I've never tried to hibernate a king so I can't comment on this.

Hope I helped out some.

King