The migrant may travel to another state.

Yes you should contact the embassy to inquire about case status.

You can have this corrected at time of interview.

Yes you must notify USCIS of any address change.

Yes the visa will be denied as the marriage will not be legally recognized.

That is unusually long. May be worthwhile to contact USCIS or an attorney to advise.

Best to apply for a travel permit with Form I131.

A W2 will be issued by your employer for H1B purposes.

This is best asked to the country embassy you will be traveling to.

Yes a LPR may act as a cosignor for immigration purposes.