There may be other things going on with your readings,or gravity. Remember, your OG was higher than it should have been all well, and you used extract so the OG should have been pretty controlled.
Extract tends to finish higher for some reason. And if it's a sweet stout there must be some unfermentable sugars in there somewhere to keep it sweet, which would raise the FG to some extent.
I would wager you're fine to bottle.