The nature and extent of your inquiry, it may be best if you consult a lawyer in private to review you case and provide options for to resolve the...

Contact specific embassy to see if you can reschedule a scheduled appointment and give reasons.

If an appointment is required, you must comply.

At least 6 months is required on first employment after receiving GC to change employers.

You may wait until your return to continue with AR11 update.

Yes, their case may be expedited, if requested.

Persons currently on a h2b visa may apply for a green card through marriage.

You may not be eligible to file I485 because you were outside the country.

This is not permitted. The derivative may not travel ahead of the principal awaiting a visa.

You may consider contacting other multiple embassies/consulates to see if they are accepting appointments.