Naturalization under 319(b) - Help Needed

[klmnl2000 18]

Hi, we're planning to apply for naturalization under 319 (b) and have several questions (some questions just generic to N400):

1. Where do we get an "A" number for N400 application?
2. Is there a generic template on how company's letter should look like?
3. What evidence to provide on "Establish that he or she will depart to join the citizen spouse within 30 to 45 days after the date of naturalization"?
4. My spouse and I are departing in about a month, can we file N400 prior to our departure?
5. Do I need to get fingerprints card before applying? Can I get them while I'm still in the US?
6. There is no Fairfax VA location on the application form. I'm planning to select Washington DC instead. Has anyone done an interview and oath in Washington DC? 
7. What to do if there is no space left on N400 to list all employers for the past 5 years?

Thanks!