Yes, both states income would be considered when calculating the premium tax credit. Per the IRS, "purposes of the premium tax credit, your household income is your modified adjusted gross income for the year plus that of every other member of your family."
Yes, it is normal, to have to pay back on the credit received if your income exceed what you estimated. The premium tax credit is determined off of an estimate but when the return is filed, the credit is calculated based on the actual income. If the income is higher you will pay back the difference.
For more information on Premium Tax Credits, see the link below:
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