You can update your I864 and have this submitted to NVC.

Yes this could cause a delay for the processing.

It varies depending on processing times. Check USCIS webpage for guidance.

You likely will not receive confirmation of withdrawal.

Depends on the nature of the offense. Best to have an attorney review.

Yes employment or school based immigration is possible.

Yes this is possible but unlikely unless certain determinations are made.

I agree with my colleague about seeking other counsel.

No you must be an adult to apply for him as Fiance.

No that’s not advisable. You should apply for I131 with pending AOS.