PHP export worked flawlessly. Simple steps for anyone else who comes across this thread:
1) Network Activate Advanced Custom Fields
2) Create Field Groups on the Main Site through the Custom Fields Menu.
3) Use Custom Fields –> Export, select all field groups, Export to PHP
4) Paste the PHP into your (child) theme’s functions.php
5) Go back and trash the fields from the main site so there aren’t duplicates.
You now have ACF fields available network-wide.
