The iterative calculation prescribed by the IRS in Pub 974 and performed by TurboTax can't always converge on an optimal result. You might be able to find a more optimal result through trial and error by indicating to TurboTax in the entry of the Form 1095-A that you were not self-employed, then trying various amounts of self-employed health-insurance deduction and finding the amount that gives you the least tax liability without the sum of this deduction and the PTC exceeding the total amount of premiums.
