3 years from date of the subsequent marriage or 5 years since residence since on GC.

This is nothing to be concerned about. Biometrics for some are waived and some are not.

The answer would be no based on information provided.

Follow the instructions of CBP and keep your travels outside of the US less than 6 months.

No, it does not matter as long as this is an accredited USCIS civil surgeon.

Continue contacting USCIS and consider consulting with an attorney.

You will need some non-availability of MC with supporting documents if no MC iOS available.

Just the address for the RFE is sufficient.

No wait until the I751 is adjudicated and consult with an attorney for review of the case.

No this shouldn’t be an issue as mother appears eligible for adjustment of status. Consult with an attorney for guidance.