One other thing that might be worth mentioning regarding 2017 and the worksheet: The reason that the worksheet produces a lower taxable result than doing the calculation directly on Form 8606 is because the worksheet allows the basis added for 2017 in 2018 to be applied to your 2017 distributions and conversions without increasing the 2017 year-end balance in your traditional IRAs while the Form 8606 calculation does not.
The reason I suggested sending a copy of the worksheet used by TurboTax if you send the 2017 Form 8606 after your original filing is because without the worksheet the IRA examiner can't validate the calculation. The Form 8606 simply includes a notation that the worksheet was used and shows only the final result.
Also, regarding the FMV of your account, the FMV will be zero at the end of 2019 if you convert the entire amount. With your modified AGI already being high enough to make your traditional IRA contribution nondeductible it seems unlikely that the resulting increase in taxable income of $1,300 would deter someone under age 50 from converting the entire balance.
