1. Cannot confirm. I believe the answer is no. See 2.
2. User's e-mail must be verified in Amazon SES otherwise SES reject it. I cannot confirm the behaviour since I use the same e-mails. I believe when one registers, the network replies, i.e. the e-mail of the plugin. For all the other requests, it is used the e-mail of the site's admin. You should have a look on the wordpress documentation. If you already got the answer, please share.
3. If you put the settings in config.php, the admin menu should be disabled automatically. See 2. or SES documentation for further infos on e-mail verification.
4. Don't know that plugin.
You're welcome.