What should I do if my green card and my passport have two different last names how can I re enter the USA if I travel?

To play it safe bring green card, passport and marriage certificate.

Can i use different state address in my i751 application mailing address ?

Keep in mind this os a marriage case and they will expect joint evidence from where you physocally live.

How long would it take for a person that has a tourist visa and is married to a us citizen to get his permanent card?

You can apply for him and them - all on separate form I-130s and I-485s

Both of those applications are his applications not yours. Filing for EAD through I-485 is sufficient.

What can I do if I made couple of mistakes in my n400 form and my interview is in about two weeks? Please help.

Go to the interview with a tyoed paper with all changes and present it to officer after you are sworn to tell the truth and before interview starts.

Spouse naturalization after becoming us citizen

You can applynin 4/2021 under 5 year rule not eligible under 3 year rule, as your spouse recently became a citizen

If the 7% green card cap has been reached in my country of Barbados before my scheduled US consulate interview of the same......

Is your case a diversity lottery case? If so, you are out of luck as of 9/30/19

Need to alien number?

File a form G-639 amd ask for your A number. Give them as much info as you know to make it more likely they will find.

Do i need to submit federal income tax return since i never filed any, because i have never been employed?

You need to file out I-864 and since you havent worked income is 0 and no current job letter is needed. You do need to submit an affidavit...

How do I get my mother, grandmother and my aunts citizenship ?

Do you mean citizenship or green card? If they are already green card holders they apply for citizenship on their own