Hello,
First of all, thank you for your purchase.
Yes, the keyword field is a required field in rules, meaning if you leave it blank and save settings, it is the same as you would delete that specific rule row.
Regarding the database fields of Youtubomatic, the rule settings are stored in a WordPress option inside the wp_options table, called: youtubomatic_rules_list
However, a much easier way to backup and restore rules is using a plugin I created for this purpose, please check it here: https://codecanyon.net/item/coderevolution-configuration-importexport-helper-plugin-for-wordpress/20541061
Using it you will be able to fully backup/restore plugin settings/rule settings for any plugin I created so far.
Regards, Szabi – CodeRevolution.