JQK

The regular EAD and Expedited EAD processing has grounded to a halt.  It is very difficult to get the EAD in a timely manner even with good documentation of need. Sorry to hear that the attorney gave bad advice. Getting the EAD and AP are free, so good to file with every application, even if not needed.

Your period of unlawful stay itself is not an issue for traveling with advance parole. But there is always a general risk when reentering the country without having a finalized status. The single-way tickets don't affect anything.  The risk is small, but it is a decision you will have to make.

But Note:

1) A Marriage case is not "K-3".

2) If you are in California, your interview may be coming up pretty soon. It may be best to just wait until you have the Green Card before traveling. You don't want to have to rush back in case you get your interview appointment.

It could be a few days to a few months. Just depends on when the adjudicating Officer gets to your case. Try waiting for 30 days, then mailing a respectful letter to the officer asking them if there is anything else you can do to help the case move forward. This may remind them to finish the case.

1) It is important to analyze exactly why it was denied. If the issue is major, it will still be a problem if you are married and file.

2) If you can figure out what the reason was and it is corrected, it may be better to withdraw the previous petition and refile. It takes a long time normally for USCIS to review the Consular denial.

A lot of this depends on the game plan you have with your Fiancé and your future together. Either way, USCIS and the Embassies are taking longer every day, so it will be a while before getting this immigration stuff over with. Consult with a lawyer.