Need to know a lot more about your case. Consult in private.

Marital discord does not make your marriage any less bona fide.

No need to ask questions, just look him up here https://locator.ice.gov/odls/#/index

No, that is misrepresentation. He did use another name as he entered under it. Engage an immigration attorney for his naturalization.

As a condition of voluntary departure, you will need to withdraw your asylum application. While you were an asylum applicant, you were not...

His employment is irrelevant to your green card application.

You file a separate I-140 for each sibling. You are not allowed to file I-130s for their kind.

Divorce would render him ineligible for an immigrant visa through you. Also, you may withdraw your I-130.

Yes. Engage an immigration attorney to represent you in this process.

It is necessary to know ALL your absences from the US since you became an LPR.