I love kings! Great first choice. They can get around 4-5' but not real fat like a python would be. Both of mine have little attitudes, but sounds like the one you're considering is quite tame. Both of mine are brats in the cage, but once they are out, they are well behaved.

An adult male would probably down a small rat, or maybe just large mice. Depends on how big it gets.

I keep dogs and cats and many snakes together with no problems. Obviously use common sense and supervise any interactions (I wouldn't recommend that anyway)