Weiss,
Re your first question. Prime itself cannot forward syslogs messages it receives. You may need to setup your wireless controller to use a secondary syslog server as your SIEM server.
Re the second, username and password is optional and only used when your mail server does not allow unauthenticated users from relaying mail.
If it allows that, you can leave those fields blank.
If it does require authentication, you should have a service account created on the smtp server for use by Prime when sending outgoing mail.