You should file Form I864 with the underlying I485 application to avoid delays

Contact the jail to inquire further or speak to him directly for next steps.

Either report the allegation or try not to worry about someone else’s situation as it likely doesn’t impact you.

Yes you may contact USCIS and request that biometrics be scheduled.

You may but will need to establish your eligibility and non immigrant intent.

Yes the ex will be viewed as the household member for I864 purposes.

No custody is required before a petition can be done.

No this is not necessary for your biometrics.

Yes use the A number from your previous GC.

No this does not appear to be an emergency basis.