Can My Attorney Spouse Represent Me/Fill Out Forms to Obtain My Green/Permanent Resident Card?

Is your spouse an attorney? It may be best to consult with another attorney to review your case.

F-1 student marrying an US citizen. How does the 90days rule apply?

It is not advisable to marry and adjust your status through marriage to a USC within 90 days of your entry into the country on a student visa.

Married With American Citizen- Applying for Green Card, but very limited income and don't have any sponsor?

No unfortunately you will need a co-signer and there are no exceptions to that.

My husband meets the poverty guideline only for this year but doesn't have the income taxes for the last 3 years for affidavit

You should use a co-signer if your husbands income is not sufficient. This consignor must be a USC or LPR who has sufficient income or assets based...

Yes your visa will be cancelled if the extension is denied.

What would be the acceptable excuses for a green card holder stay outside the Us for a year and three months ?

Medical reasons are acceptable for prolonged absences from the US.

For the citizenship application, Do I have to mention moving traffic violations on N-400?

No traffic violations do not need to be disclosed.

Address hustory; 8 days spent abroad while residing in the USA.

Brief travel does not need to be disclosed on the I129F.

How much letters comes in brothers sponsor visa ?

Please rephrase your question as it is unclear which letters you are referring to.

Yes you may and it is best to send a written request with the basis for it. Good luck.