I'd like to double this recipe. Do I also need to double the brining time and the cooking time? Or just all of the quantities? (Sorry for the misp...

No, you don't need to double the brine time or cooking time because pork belly is a flat piece of meat, so it will be the same thickness. If it is very thick (my 5 lb pork belly was only slightly thicker than my 3 lb) you could brine it an hour longer. As far as cooking it, you slice and then cook it, so the cooking time won't change. It sounds delicious!!