The total mortgage interest deduction will drastically drop when you have to limit the amount of deductible interest due to reaching the $750,000 mortgage limit. There is no way to get around this. You can only claim interest on up to $750,000 of mortgage principal. No matter how you look at it or how much you are losing, that is all you can take.
To determine the amount of interest divide the maximum debt limit by your mortgage balance, then multiply the result by the interest paid to figure your deduction. You indicated that your total mortgage amount is $2,000,000. Dividing the $750,000/$2,000,000 gives you .375. Multiply this by the amount of interest that is deductible. If your total interest is $13,000 then the amount deductible ($13,000 x. 375 = 4,875) I am not sure if these are the actual numbers in your case, but they are the numbers I picked out from your question.
