Today I went to Home Depot and took two trips to a local plumbing shop, trying to find some combination of fittings that would work for the galley faucet. This is the problem with brick-and-mortar stores. Your choices are limited to whatever they have in stock.
Here’s what I’ve got so far. These are the drop elbows I was talking about, mounted on a piece of marine plywood whose depth is TBD. The faucet’s water supply connections are 3/4″ female. But it turns out these drop elbows are 1″ female. So I had to add a face bushing to the 3/4″ nipple to make up the difference. And that, of course, is less than ideal. That’s one more point of potential failure.
Later I found these 3/4″ SharkBite drop elbows on Home Depot’s website. So that would eliminate the need for the face bushings. It’s not in stock, so I’ll have to wait for it. I can’t secure the plywood until I dry-fit everything together, but I should be able to figure out the drain and pump by the weekend.