So I quit. I went to "deactivate account," waded through the "But your friends will miss you!" photos, and completed the form.
Then I was going to log in as B, to see how much of my information was still there, but LastPass logged me on again. FB said, "Welcome back! Your account has been reactivated."
So I RE-deactivated my account, turned off LP, and logged in as B.
A search for my name came up with only other people (with the same name). I did find some photos with me tagged in them, but I guess they're not searchable. I don't think there's a way to keep other people from posting pictures with me in them. And they can always tag me without a link to me. Sooo...
I'm reconsidering Twitter. That is, I may keep it. I'm still working out my whole online presence, and it may include a blog migration, so stay tuned.