Resolved.
Perhaps this is only for Multisite instances of WordPress, I still have all of the above factors in play: php.ini, .htaccess and wp-config.php but I also went into the root site as the super-admin user.
- Get to the Network Admin page. In WordPress 3.1 this link is found on the top right of the admin screens. It toggles between Site admin and network admin.
- Click on “Settings” in the admin panel on the left hand side of the screen.
- Near the bottom of this page is a section called “Upload Settings”. Find it.
- There is a field for “Max Upload File Size”. The units are KB.
- Convert your intended file size into KB. (100MB = 100 * 1024 * 1024KB = 104857600KB)
- save changes at the bottom and test for sanity.
https://wordpress.org/support/topic/changing-file-upload-limits
http://www.wpbeginner.com/wp-tutorials/how-to-increase-the-maximum-file-upload-size-in-wordpress/
