Agree with above and this is was covered in the first packet of info I received and the update I received when I had my C&R.
No idea how you will put all that together after 20 years. Especially seller info.
If you renounce your license you are no longer responsible for the records and may destroy them. If I were in your shoes I would cross my fingers, surrender, and re-apply after a bit and hope for a fresh start. Not that I am suggesting you do that as it is more than likely breaking a few more laws, but if I were in your shoes I would probably take that route.
I made a couple of clerical records after I first got my C&R, specifically the "FFL" record book I used requested slightly different info than I actually needed. I was able to contact the first 2-3 people I had transactions with and gather the necessary information without any problems though. I think it was their home address or maybe drivers license number or something that I had wrong.