Unauthorized employment is waived through marriage based adjustment to USC.

It depends on whether you plan to travel while the case is pending.

Depends on length of trip. You can indicate and provide explanation of his visa status while visiting.

It should be accepted as valid if original.

No the applicant must be in the US to adjust status.

Departing the US would have consequences upon reentry. Consult with an attorney to understand more.

Best to speak with an attorney who specializes in German immigration law.

No it appears the case was withdrawn and cannot be reinstated.

Best to consult with an attorney for guidance. Good luck.

You will require a new petition as your LPR status has been abandoned.