I had some confusion too because in order to retire early, our battle plan relied on ACA coverage. We enrolled during an early version of the plan. You were allowed to go under the minimum income with a valid excuse, but if you went over the income cap you had to pay (re-pay) the full premium amount. And I didn't recall any option for IRA contributions.
For 3-years we hit the middle of the income range, and our tax credit paid 100% of the premium. Then, year-4's dividends and cap gains pushed us over the income cap. However... the rules had changed and there was a different calculation to the credits limiting you to paying less than a certain percentage of your income for health insurance. So I only had to re-pay $3,200.
Maybe that change in the plan could be a loophole for you?
