You may try again and explain what led to your oversight of required signature.

You can withdraw I539 for husband now. File another I539 for son.

You must respond to the RFE. Also, present your own side of why you qualify. Typically, failure to reply would be ground for denial.

The city where you live at filing of I130.

It depends on a lot of factors. The estimate is about 2 years.

In general, USCIS does not contact EB2 NIW recommendation letter writers.

Yes, a USC petitioner can petition for a spouse for permanent residency, even though FN spouse if out of status.

Variation of signature(s) on USCIS application does not cause delay of application process.

A LPR may file for AOS for overstay spouse, but spouse cannot adjust until in status. Spouse may be able to adjust when LPR spouse naturalizes.

Untimely filing of renewal application for EAD does not get automatic extension.