Okay, here are my thoughts.
I agree that you can use the average of first and last balance method. Your interpretation of the first requirement is correct.
But the phrase "the first day of the year that the mortgage was secured by your qualified home" has only one possible meaning. It is not ambiguous at all. It clearly means the date that the mortgage was originated, which was in May. Your alternative interpretation is an impossible stretch. By saying it's January 1 you are essentially putting a period after "the first day of the year" and deleting or ignoring "that the mortgage was secured by your qualified home." Your reading of the instructions for line 1 is clearly colored by your obvious burning desire to include some zeros in the average. But you can't do that. You never had a mortgage with a zero balance. You don't get to count the days or months before you had a mortgage.
You may also be putting too much weight on a vague comment by "a tax professional" who apparently did not prepare your 2022 tax return and probably did not do a detailed investigation of the facts. "Seemed too low" sounds like an offhand comment after a quick glance, not a professional conclusion based on a careful study.
