Sorry, the limits do not stack. $8550 is the combined maximum as well as your wife's personal maximum. She can contribute $8550 and you nothing, or you can each contribute $4275, or you can divide the limit in any other way that makes the math work.
If you leave the excess in the account, you will pay a 6% penalty this year and every other year until the excess is resolved.
One way to resolve the excess is--assuming you are eligible to contribute next year (2026)--contribute no more than $8750-$4300=$4,450. The excess from 2025 will be applied to the remaining "space" under the 2026 cap. But this will cost you $258 in penalties.
The other, more conventional way to resolve it is to contact the HSA bank and ask to remove $4300 from one of the accounts as an excess contribution. This is a special procedure and probably requires a special form, it is not a regular withdrawal. The bank must return the excess to you with any interest it earned. The interest is taxable income on your 2025 return, but you won't pay the penalty. Then you can contribute the full amount ($8750) for 2026.
MFS will not help at all, you will still have a $4300 excess, plus all the other lost deductions and higher tax rates of filing MFS.
