2) Is the username allowed symbols like $ & _ in them? Or is it just numbers and small case letters. This will help me be more sure of my username.
here, go through the list yourself (the link to the .csv with all accounts is in the first post): http://forum.bitcoin.org/index.php?topic=19576.0
For account recovery they are asking for "<11>Send the account number(s) and amount(s) you used when depositing into your Mt.Gox account." what is this referring to?
that would be the UserID (column a).
best of luck to you.