No obtaining unemployment benefits should not impact your application.

Yes this is possible but your case requires a consult with an attorney for guidance.

Can I apply for a travel document i-131 while my i-360 is pending?

Possibly but not necessarily advisable to travel without consult.

N400 question regarding arrested, cited or detained?

Yes you should answer affirmatively and provide details if requested.

You should always answer truthfully but this should not detrimentally impact your application.

Yes you may but be sure to resend with proper documents and fees.

Unfortunately you are not adjustment eligible based on sibling based petition. Seek consult with an attorney for guidance.

Does only the sponsor fill out a I-864 Affidavit of support ?

No, the petitioner also must complete I864 regardless of income.

Do i use I864a?

The sponsor would use the I864 and the spouse of cosponsor would file I864A.

Can my spouse, who lives overseas, stay here even though I-130 has not been approved?

Yes, you will need a copy of the I 130 receipt. You should consider consult with an attorney for guidance.