Snapshot unable to make backup (timing out maybe?)

Hi, I have added some 50,000 "dating profiles" to my site and I believe this may be creating a timeout and making it impossible for Snapshot to create a backup. I tried referencing https://codex.wordpress.org/Editing_wp-config.php#Alternative_Cron to see if this could help. I added to my wp-config.php file:

define( 'ALTERNATE_WP_CRON', true );

define( 'WP_CRON_LOCK_TIMEOUT', 240);

...But still no backups are happening, and there are no error messages...

Help! I really need to backup this site...