If you file N400, they will eventually put you in removal proceedings. there, you will be able to challenge the denial. If you win, your CG will be reinstated. If you lose, you may file to readjust if you are still in a relationship. If no other relief is available, you will be ordered deported. hence, the best thing to do is to seek help from an immigration attorney. I am sure FL has some to offer.
You need to hire an immigration attorney to handle this for you. There may be a way to argue that the i751 should not have been denied (or that in fact it was never denied as it is still pending) but that is not something that you can do on your own. It is likely that this argument will need to be made in immigration court where your case will probably end up.
I agree with my colleagues.
Disclaimer: The information provided here is generalized and should not be relied upon as legal advice. This communication does not create an attorney-client relationship.
If you received a written denial of your I-751 then it would appear that your case has been denied and that the computer may not have been updated or the clerk you spoke with is giving you incorrect information. You are entitled to have your application reviewed in removal proceedings, though it seems there are other issues which also need to be addressed. You are also entitled to proof of lawful status while this is all going on. Consult with an experienced immigration attorney who can review your case and advise you how best to proceed.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Call +1-561-478-5353 to schedule a consultation with Mr. Devore.