Hey @Alex - I figured it out! For anyone reading in the future – the “HTTP Header” option in the tutorial in no longer necessary (there is no field for it). Instead, as long as you are previewing both your web container and server container, they should communicate.
Regarding my second point in the original post, this is still a bug/issue. The “Name” and “Transform” fields become empty once the GTM page refreshes. This doesn’t seem to be an issue with the Facebook CAPI since the Stape FB template automatically hashes the data, but I can see it being an issue otherwise.