I removed the tension nut as Joe described. There was indeed a washer with one tang. When I took this washer off it looked like this
.
This is a part of the handwheel, or at least seems to be, at least there's no part that can be pulled off.
The Handwheel spins freely, but not in any shaft. It can't be pulled out of any shaft. If there's any place it could be pulled out there are three of these screws.
I haven't tried very hard with these screws, but they are stuck in place and seem to be made of soft metal, as even my feeble attempts dented them a little. I don't know how I'd get these out.
As for the presser foot, the presser foot and needle bar are both currently off of the post right now, so no worries for the feed dogs!