Hi James,
Regarding your questions about activities:
1) You are correct that ContactId is not currently available to be included in these activities. We are working on getting them added in a future release. Email address is available on these activities and can be used to link the activity to a specific contact.
2) Currently only hard bounces are included. We are working towards adding both soft bounces and the reason code in a future release.
3) This has not been reported previously, thanks for sharing.