It will cook fine, as long as you leave it in long enough and don't take it out too early. Although if you are cooking it in a crock pot, I would suggest maybe trimming off some of the excess fat first since it can be really greasy in one of those, as opposed to something like an outdoor smoker where the fat can melt away and drip off during the cooking process. In addition, I would perhaps cook the roast by itself, so you can drain off the excess fat and moisture first before adding any additional sauces and seasonings.
Usually if I am using a crock pot, I will go with a leaner cut like a bonless ribeye roast, or maybe even a pork loin.
You certainly could add cider, though I am not sure how much of a difference it would make considering all the liquid and fat the roast is going to give off. I've heard of adding an acid such as cider, or wine or tomatoes when making something like a bone broth, because the acid reacts with the calcium in the bones to help leech out more flavor.