Please see latest comment:

I've poured a ton of time into troubleshooting this, including reaching out to Litmus support, and am baffled. I'm specifically look at the two iPad tests. This is a centered layout that is fine in Outlook and Apple Mail, and with iOS versions working correctly per media queries.

The iPad layouts are left-aligned (instead of centered) and only filling 669px. There's nothing in the code resembling 669px.

Max & min zoom set to 1:

Just initial scale set:

Nested table in the email (works!):

Any thoughts? Help!