Hi Brad,
Thank you for sending the file. There is a bug for Send-to-Excel with Equations when the Single Owner financial model uses time series PPA price multipliers. We will fix that for this fall's release:
github.com/NREL/SAM/issues/694.
The only workaround is to use the weekday/weekend schedule instead of the PPA mutlpliers, or to manually modify the Excel spreadsheet after the export so that it has the correct values in the Net PPA Revenue row of the Cash Flow worksheet.
Yes the IRR, NPV, PPA price, and other financial metrics can be very sensitive to small changes in the financial assumptions. The size of debt changes both the initial investment cost and the annual recurring costs, so those metrics are especially sensitive to that assumption. You can compare the cash flows for different debt sizes to see what is causing the difference in IRR.
Best regards,
Paul.