15 square meters isn’t the same as 15m×15m, it’d be a little smaller than 4m×4m. Still a big hole.

Nice.

You don’t actually need to continue your taper through the bridle joint; just start your taper behind the joint.

Yep, you just have to set Keep as your default note service in the Google Assistant settings.

Shared notes in Keep sync very quickly in my experience as long as you have a reasonable internet connection.