Hello,
1. I am not sure why this is the case. Is it possible for you to set the server time to your local timezone? What happens then?
2. If you have already set up a trigger for the main cron job task, then that is enough. As long as WordPress is being triggered then the Airdrop cron mechanism will also run. It will execute any past (pending) airdrops, at most one per minute, then it will check for any future airdrops again once per minute and will execute any airdrops whose time has come.
3. Regarding the issue with non-matching collations, this is something that you should address before anything else. It is very likely that it causes several user-related issues and yes, it is also likely that it is what’s preventing you from running airdrops for specific roles. The issue might have been created by a plugin that created tables manually without first checking the result of $wpdb->get_charset_collate(); (https://developer.wordpress.org/reference/classes/wpdb/get_charset_collate/)
with regards