you won't have the update using slow ring, you need to launch the Insider app again and change to fast ring if you really want to update.

Otherwise you won't get the update for quite sometime on slow ring, sometimes they even skip updates.

I'm on 10166 as well, only upgraded like last week so feeling like using it for a few more weeks before another upgrade, I may be skipping this build. I only re-enabled the upgrade because I thought a new one is not coming out soon, I usually skip one or two builds one.

I have the SD card problem you mentioned as well, it is something with build 10166, in the release note of 10512 they mentioned that it's fixed, so if that is something important to you you can upgrade it. The problem has not occurred for quite a few days already so it's not a big deal for me.