If you converted a Traditional IRA to a Roth IRA, that is income on your tax return. That is also income for purposes of the Premium Tax Credit ("ACA subsidy"). So yes, it is quite possible that IRA conversion increased your income to disqualify you for the credit. If you look at Line 3 of Form 8962, that shows your Household Income for purposes of the Premium Tax Credit.
You can try filing as Married Filing Separately. When you do that, 50% of the 1095-A gets allocated to each tax return (enter the full amount of the 1095-A, and then on the following screen say it was shared with somebody that is not on your tax return).
Although you will still need to repay some of the Advance credit, in some cases the amount you need to repay will be reduced. However, filing as Married Filing Separately often results in higher income taxes, so you may want to test it out both ways to see what is the best result.
In the event you are self employed, you may be able to contribute to a
SEP (retirement account) by October 16th to reduce your income.
