Contact USCIS to have this rescheduled as normally should not happen.

Yes the name of sender can be different than party filing.

Refer to the visa bulletin in F4 category for guidance.

Any other previously issued cards should be brought.

No not if your permanent residence hasn’t changed.

Write to the USCIS service center handling the case and request it be withdrawn.

Contact the Turkish embassy for guidance.

Depends on what basis you had to apply for I131 and the reason for denial. Consult with an attorney for guidance.

One letter for the couple is sufficient with both signatures.

You may indicate your marital status but can file separately for tax purposes.