I am getting laid-off on Dec8 & plan to eFIle for 4-6 months COS B2 Visa on Dec7.

Please let me know when exactly I should submit my supporting documents to USCIS, should it reach them on Dec 8/ I can post/mail them by Dec 10/12?
please confirm the Documents to submit:
1. Bank Statement (How detailed it should be? How much money to show?)
2. Letter - Explaining why we want B2 Visa (Would it be possible for you to provide me some examples?)
3. Brief itinerary - How detailed it should be?
4. Copy of I-94
5. Documents showing permanent home in home country
6. Flight tickets -(one way - )
7. Which health insurance we need to buy while staying on B2 visa (normal Tourist insurance or COBRA?)

Any precaution or any suggestion for e file COS to B2 Visa application.

KR, Sanjay