I would be surprised that there is a threat of a tax audit. I have done something similar, though not with student loan interest.
Determining the last number requires a bit of spreadsheet-fu
That isn't unusual for 1098-T and 1099-Q calculations.
I have found that even Turbo-Tax has problems with the calculations, due to the fact that the school my ...
The 2019 version of the IRS Publication 970 was just recently released, and it clarifies that you have to take the distribution from a Qualified Tuition Program (e.g. a 529 account) in the same year as the qualified education expense.
What is the tax benefit of a QTP?
No tax is due on a distribution from a QTP unless the amount
distributed is greater ...
529 Contributions are not tax advantaged, just the earnings. If you put $1000 in your 529 account, then immediately use it to pay your loan, you don't get any benefit. If you put $1000 in an index fund and wait a year, you could end up with (say) $1050, and that extra $50 is non-taxed.
Your job's $200 yearly contribution is the real reason to do this. (Also,...