Currently, the Move it to the Trash if the spam score is at least option does not affect the Apple Mail - Rescue Good Messages script. If you want the rescue script to move blocklisted messages to the Trash you would need to edit the script, changing the line:
property pMoveBlueMessagesToTrash : false
to:
property pMoveBlueMessagesToTrash : true
I don’t think so. You can verify in the Log window what SpamSieve thinks the sender is and whether it classified the message as spam because of the blocklist.