They wrote me back very promptly and suggested I take pliers and bend the connecting piece of metal (A). From the beginning, I knew that this piece of metal was a big part of the problem, but it's a very hard metal. I had even tried to pull on it with my hands, but it didn't budge. I was worried that the force I would need to use to bend it might put too much stress on the wheel. I didn't want a piece of wood to split or to compromise where the metal is soldered together. As it turned out, pliers were not very useful. In the end, my husband just pulled on it while trying to brace where the piece is joined to the other treadle. I winced as the wheel shuddered under the force, but my husband managed to bend the piece of metal enough to keep the two legs from knocking into each other.
Having made that adjustment, I was able to reattach the right leg to its treadle as intended. It's still a good thing that I shaved a little wood from the right treadle (B). Even with everything put together correctly, the left treadle leg would have brushed against the right treadle. I think the hole in the left treadle should have been drilled just a little to the left. It's amazing how narrow the margins for error are on what is essentially a simple machine.
After all of this tweaking, not to mention a lot of silicone spray to remove all of the squeaks, my Joy is now running like a well oiled machine. I'm a little traumatized by everything I had to do to get this brand new wheel running smoothly. I haven't experience a lot of joy with my Joy yet, but hopefully that will change. I think I just need to spin a few skeins of fun yarn to get over my mixed feelings.