As I understand it, using the original purchase price you have a loss
Using the lower FMV at time of conversion you have a gain.
Therefore
I have seen this before and always recommended professional help. The bottom line is, the TurboTax program *can* *not* *correctly* handle this situation no matter what you do. I've tried different scenarios myself last year with TTX 2018 and could not get a correct result. But if someone figures it out, it sure would be helpful to let folks in this forum (such as myself) know.
One thing I've never gotten clarity on is for someone with your specific scenario, where you have a gain with one cost basis, and a loss with another. The best information I can find on which cost basis to use is in IRS Publication 551 page 11 at https://www.irs.gov/pub/irs-pdf/p551.pdf. But it doesn't cover what we need it to cover. So the best information I can give you, is "seek professional help". You've got two days before the filing deadline. If you will be getting a refund, there will be no penalties for filing late. But if you owe the IRS, you "will" pay interest on what you owe if you pay after July 15th.
