I have the same smoker as well. It usually takes me 4-5 hours to do 3 chickens (split in a half) at 250 degrees. As far as the pork butt, I’ve done (2) 5 pound butts (bone-in) in about 12 hours at 225 degrees. You must let the internal temp reach 195 degrees in order for meat to pull. I always leave the water pan in and full. The water contributes a great deal of moistures to the pork butts. When I cook chicken alone, I usually use the water pan for the first 2-3 hours of cooking, and then I remove it and turn up the temp up to 300 degrees to crisp up the skin (just a personal preference).
I hope this helps.