1. KCC no longer has any role to play in this process, it is now between your FO and the embassy. The FO is supposed to forward the case file to the embassy after your AOS approval. It looks like they're not doing that without the right prompting. Contact the embassy again and ask them to contact your FO to request your case file, KCC will not be scheduling the interview appointment, the embassy schedules the appointment once they have the case file.
2. Yes initiate a congressional inquiry to request they contact your FO (not KCC), and for your FO to forward your case file to the embassy for the FTJ.
3. Don't wait for the I-824 receipt to initiate the congressional inquiry, remember it currently takes a while to get the NOA. They will get back to you to let you know if they need the receipt or not.
By the way, which is your FO?