As long as he has previous GC and receipt of extension, he should be okay to return.

Yes you may apply for EAD after 150 days.

If based on fraud, could have immigration consequences.

You should indicate in the affirmative.

Contact NVC again to request update on your case.

You should not need secondary inspection after becoming a USC.

There is no legal limit but best to avoid multiple requests.

Yes you may request expedited processing.

An expungement will not provide any value for immigration purposes.

This can be corrected at time of interview.