Alright, finally got an answer on this directly from TurboTax after being on the phone for over an hour. I was instructed to delete the first two 1098 forms and leave the last one (from the lender I had on 12/31/19). He stated that it is the loan balance as of 12/31/19 that is relevant to the mortgage limit (seemed a little odd to me since others have stated that it's the balance as of 1/1/19 that matters, but the balances on both dates are nearly identical for me).
I then added all of the interest and property taxes from all three 1098 forms and entered the respective totals in the appropriate boxes. He said that if you enter each 1098 separately, the system will automatically treat each one as a brand new mortgage. Strange that it never said anywhere in the help sections to do that (you'd think this would be a common enough situation that would warrant written instructions), but all of the numbers and calculations are now correct on my final tax forms.
