In your case, the extension letter itself, is of little use since it must be used with an expired 2 year Green Card. A decision for Removal of Conditions could take up to several years. I have seen cases take almost 4 years. At the end of the 3rd quarter FY 2023, there were still more than 217,000 (I-751s) still pending in the system. They are processing only about 30,000 I-751s per quarter. I would file an N-400 as soon as eligible. The sooner you file, the sooner you will be rid of USCIS. Good luck.