give it more time. Bigger beers need more time to finish. Plus that yeast will work better above 65, It hasn't yet been 3 weeks. The last few points of gravity take a long time to come out. (btw, all the info in the post is good)
I'd bring the temp up, and swirl the carboy (this should cause some co2 to come out. Don't remove the airlock, just swirl. One way of bringing the temp up is to put it in a room with a shirt or towel wraped aroudn it. If that doesn't do it much, put an incandecent light on in the room, that will heat the air and thus carboy.
Give it another week and let us know.