Consult with a family law attorney to obtain a restraining order as my colleague indicated.

No your mothers spouse would not be included.

Best to consult with an attorney to discuss your entire case history.

No it does not appear to be eligible.

You can submit a FOIA request for your immigration history.

Yes this lack of filing would be a hindrance to acting as sponsor.

Yes this is very normal given date of filing. Be patient.

Your niece could apply for a student visa on her own.

It depends on the nature of the filing and whether applicant is in the US.

Contact USCIS again as the case appears to be outside of processing times.