Sounds like you hit one hell of a plateau... the bane of us all. The meat will reach a plateau where it starts slowly breaking down all the fat. Your IT will totally level off (for hours depending on the size of the butt... plus each one cooks a little different). The IT may even drop a little bit. As long as your smoker/oven is still cooking at the right temp, this is totally normal. The key here is to NOT kick up the temp of the smoker/oven because then you don't allow all that fat to render out and you end up with tough pork (a butt is by nature a tough piece of meat). When cooking, I always budget 2 hrs per pound. This does not mean that every butt will take a full 2 hrs per pound to cook, but that is the time I budget for it when planning a meal, etc. (Also of note, you can wrap a butt in foil, wrap a towel around it, and throw it in a cooler and keep it piping hot for HOURS AND HOURS until you are ready to take it out and pull it... so I always like to err on the side of finishing the butt long before eatin time.)
Just realized I'm talking in circles now. Bottom line: once the meat plateaus, don't kick up the heat. Just close your eyes and let it do its thang.
In terms of the pink, you will certainly have a good deal of pink along the outsides. This means you have a great smoke ring. Safe temp for pork is 165, so as long as you're past that point it is totally safe to eat. HOWEVER, you do have to get IT up to around 200 if you want a fall off the bone, tender butt.
Keep at it! (BTW, I usually smoke butts no more than 7-8 lbs so that I don't have to cook quite as long. Two 7 lb butts will cook faster than one 10 lb butt, so if you're going for more quantity, I still would just get 2 butts of 7-8 lb size.)