Remove the top, and use a high temp silicone caulk around the inside. It will seal the top to the ceramic, preventing the leakage. Also, make sure your vent bolt is tight and somewhat difficult to move. Do not use JB Weld, as it may produce harmful gasses that will permeate your food.
Remove and seal the bottom draft door also, as you are probably getting to much air movement through the smoker. I use lump, and get a 20-24 hour burn out of a 15# bag.
Finally, you need indirect heat in a smoker, so a water pan used with or without liquid provides that. I use apple juice sometimes, or another fruit liquid, if I want. But a little water helps to keep the meat moist.
My only gripe with my cypress, is the thermometer is way off. I use a DigiQ and have seen the temp vary by as much as 50 degrees. I would recommend using one for any smoker, their not cheap, but to spend 18 hours on a cook and find out the hard way that the thermometer is no longer working properly will ruin your day.