Yep, pork butt/shoulder is a pulled pork piece of meat, not a slicing roast. You can do it, but it'll be fatty and tough.
I don't add water/broth/stock to most meat. The moistness you're getting is from breaking down of the fat, not so much the water. The water evaporates almost as quick as you cut into hot meat. In order to get the fat to break down it needs to get to 190-degrees, so you try to slowly get to 190-200 and hold it long enough for the internal temp to get there. Then you usually take it off the coals and let it rest with the lid closed (don't open the lid.
With dutch oven cooking I tend to get the oven hot, sear the roast, then put the lid on with the appropriate number of coals top and bottom.
Pork butt/shoulder can be shredded or rough chopped (big chunks). If you rough chop it into big chunks and put some more coals on the bottom to get the oven hot again you can make carnitas. You fry the big pieces of fork tender pork and you have some amazing carnitas. If I know I'm making carnitas I'll cook the roast with a cut orange, onion and cilantro. That gives the meat a really good flavor before refrying it. You can flip the lid over and use the inside of the lid to heat your corn tortillas. A little diced onion and cilantro is all the rest you need to make amazing pork carnitas tacos.