I wish the topic did not say bug, because these are not actual bugs, and the settings you miss have been changable on previous Nokias as well 
For example, the situation was quite similar on my previous phone, the E72.
1) Start mail application (Menu / Applications / Mail), go into Settings. Select your account. Go into mailbox settings. The setting "My mail address" is what you will send out on emails if you send them from your device. Go into "Advanced mailbox sett." (bottom), then either Incoming or Outgoing settings. You can change your username there.
2) My N8 picks up the changes the next time the phone updates the mail folder. I use Mail for Exchange and two IMAP accounts. I can force a manual update if I want the changes visible right away, or just wait for the next schedules update.
3) Please see point 1 on where you can set these kinds of things like port number for SMTP. In the "Advanced mailbox sett." dialog there is a possibility to set port number, etc.
I do have to admit that the Email Wizard is annoying for users who know exactly what and how they want to setup. I usually try to get through that as fast as possible and then set the rest of the settings by hand.
