If you maintained family HDHP coverage and you yourself were not covered by Medicare or any other disqualifying coverage, your eligibility to contribute the full $9,300 to your HSA was unaffected. Given that you were unaware of the lookback period for your wife's Medicare coverage, it seems likely that you would not have changed to self-only coverage and you were eligible for the full $9,300 contribution.
Only actual excess HSA contributions are eligible to be returned, and it seems that you made no excess contribution. A distribution of a purported excess contribution that is actually not an excess contribution constitutes an ordinary distribution no matter how it is reported on the Form 1099-SA. You would need to enter the Form 1099-SA as having code 1 in box 3 and $0 in box 2. (You might have to explain this to the IRS.) As an ordinary distribution, you can apply the distribution to qualified medical expenses paid in 2024 to reduce the taxable amount of the distribution.
Your W-2 is correct. No correction to your W-2 is needed. Even if there had been an excess contribution to your HSA, no change to the W-2 is to be made. The excess contribution would simply be added to your 2024 income on Schedule 1 line 8z after indicating to TurboTax that you did not have family HDHP coverage for the later months of 2024. The earnings distributed with the returned contribution would also appear on line 8z.
You do not get a deduction for HSA contributions made through your employer because your employer has already excluded this amount from your earnings. You should see $9,300 on line 9 of your Form 8889 because you had family HDHP coverage for all of 2024 and you yourself had no disqualifying coverage in 2024.
