I moved in 2021. The old mortgage was smaller, pre-2018 and $1mm . The new mortgage is larger and $750K . TT is spreading all interest across mortgage 2. How do I fix?

There are two errors here that is causing my write-off and refund to be lower than it should be.  First, interest on the old mortgage is being spread across the new mortgage balance which is diluting how much I can write off.  Second, interest on the old mortgage is being capped at $750K when it should be $1mm.