I always warm my bows up with partial draws, if its been unstrung for an extended period I may take 30 minutes to work it up to full draw.
Hickory is one of the worst woods as far as humidity goes, in high humidity it can absorb moisture and lose draw weight and get sluggish. On the other hand it really
shines in dry conditions
No finish is water proof at best the finish slows down absorption of moisture, you can wax your bow as an additional layer of protection,
good ol turtle wax works fine
Yes lots of folks make D bows out of a myrid of different woods.