If you notified healthcare.gov of your change of income and cancelled your benefits when your wife started receiving benefits, your PTC and Form 8962 should be calculating correctly.
Does your 1095-A accurately reflect the months from January through August? If not, you should contact healthcare.gov for a revised form. Did you enter in TurboTax that employer coverage was only August through December?
There are limits on what you have to pay back. Here's some info on PTC you may find helpful:
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