Can you not go in person for the visa to the Detroit office? I'm assuming that you can't since you say it's 400 miles and you would mail it, but would drive 14 hours to Buffalo if you stay in that office. So I guess you're not in Florida then. Must have read that about someone else.
Now I'm wondering if you can go in person to the Seattle office. Is it a fact that you can't drop off your passport at any of the satellite offices? I was just assuming you could..... I'd rather not mail mine as then I will be in Canada without a passport, which means I can't get back into the USA until they send it back. Probably I wouldn't need to, but you never know.... I was going to apply for one of those passport cards before I left, but then you had to send in your passport with the application, and I needed it to get into Canada and there wasn't enough time beforehand. Also, I worry the passport might be lost when mailed back. I heard they just mail it and don't register it or use a courier service. Although maybe there's a way to do a pre-paid courier envelope that would work. But since I am in Canada, I don't think I'd be able to get one that could be sent from the USA. I thought I read someone else saying they couldn't do that for some reason (you had to have an account or something). I certainly don't want it mailed by regular mail. A few months ago, it took a priority mail envelope (only filled with documents/mail) 3.5 weeks to get from Seattle to Vancouver. Can you believe that? Also someone mailed me a package from the USA 6 weeks ago and I never got it. I don't trust the mail anyway, but when it goes over the border I REALLY don't trust it.
You will do need to use one sticker. It says to "save" one for the end of the file process or something like that (maybe for sending in the passport). There are 15, so hopefully we won't be needing to use ANY of them.