Don’t worry about over-estimating your income – that’s not nearly as bad as UNDER estimating you income! But you could perhaps get a less expensive plan (a larger subsidy) so it’s important that you report the change immediately.
Use this link to do that: https://www.healthcare.gov/reporting-changes/how-to-report-changes/
And honestly, if you now have NO income and are living on savings, check out your state Medicaid plan or other health insurance support that are based on income. As well, you might be eligible for food benefits and utility subsidies. All of that will help replace your lost income.