1) My RSS feed reappeared like before but some do not work and none of them show more than 25 of the previous feeds.
I believe some don't work because either they "expired", the URL changed, or the article was removed. I'm sure the number appearing is due to the time you have the preferences set to remove feeds.
How can I get the old entries back in Mail?
I would think you have to go to the RSS section of Mail's preferences and set the time for it to remove feeds.
2) You said there was an esier way to fix the email in limbo problem. How?
If an email is "stuck" in the Outbox, you should be able to remedy that problem like this:
1. Quit Mail if it's running.
2. Go to Home/Library/Mail/Mailboxes/Outbox.mbox
3. Delete the message inside Outbox.mbox
4. Go back to mail and restart it.