It lives! Hope is not yet lost. My car was parked on a public road and fortunately had not yet gotten towed, so I just went for it. I did what was suggested, and surprisingly not so much as a drop spewed out of the plug holes, although the car had been sitting a week at this point, so maybe it's not...

If it were me I would proceed by refilling the oil to the proper level and then I would remove all of the spark plugs and and crank it over for a minute or so. If there are residual oil pools in on top of the pistons it should blow it out the spark plug holes and it could be quite messy. After that...

tl:dr - I accidentally put 10 quarts of oil in my V70. Now it won't move, makes a knocking sound at idle and dies when I let off the throttle. I drove only a few miles with this much oil (it drove great at first, then overheated quickly) and I've only started it twice since the knocking sound appear...