There should be a notification within an hour or less, it’s not instant because if there are many users to notify the listing author will have performance issues during the listing submission (e.g. if there are 100 emails to be sent at once).
1. If you mean making it more frequent it’s not possible at the moment, the minimum built-in recurring period in WP is “hourly”. But the hourly check may occur after 1 min, the 60 mins is the maximum delay (if a new listing is added right after the previous hourly check).
2. No, HivePress servers are only used for checking new theme/extesion updates and loading the extension list in HivePress/Extensions section.