You're gonna get mist out the front of the enclosure, Mist king or any other brand.
The mist cools the air and causes a downdraft. Like a thunderstorm, only on a much smaller scale. You could try putting a small throw rug in front of the cage, or a small fan blowing over the area to help it dry up faster. Or both.
If the tubing is cut straight, and fully pushed in, it is almost unheard of for the fittings to leak. Not saying it is impossible. I have had one bad fitting in the hundreds I have used over the years. But in the rare instance I have had a problem, only once was it due to the fitting. All other times it was because of installation error.
As long as you used the tubing cutter supplied with the mist king and not a pair of scissors, and made square cuts, my guess is the is not fully pushed into the fitting. Sometimes it is difficult to get the tubing properly seated, depending on the space you have to work in. The tubing should go into the fitting a good quarter inch.
Once you have it leak free, it should remain that way for, well, forever, unless you disconnect the tubing for some reason.
I have three separate mist kings currently set up, and no leaks.
I couldn't imagine going back to a time when I kept a cham without one. They really do simplify your life, and improve your cham's life.