So sorry for your loss. I agree with the others who encourage you not to make any huge decisions right away.
As for what the ideal taxable income might be for ACA, that depends a lot on what you want to spend and how much you have in savings that wouldn't be taxed upon withdrawal (mainly existing basis in your taxable and Roth accounts).
Why your expected spending matters: to a first approximation, your income during retirement will be equal to your spending. The more you spend, the more you'll need to withdraw, and the withdrawals will often count as income for ACA purposes.
Why your existing basis matters: At this moment you have some amount of savings that will not be taxed upon withdrawal. This might include your cost basis in taxable shares (including the full purchase price of shares you buy with your life insurance money) or Roth contributions/conversions that you made already. You can cash in on this basis to push your income below your spending, but this amount is fixed-ish*. Once it's gone, it's gone. Use it wisely. Suppose you have $500k of such basis at the moment, and you expect to live another 50 years. That means on average you can sustain an income of $10k below your spending each year. If you want to adjust this for inflation, you might want to start a bit lower than $10k and bump it up a notch each year.
Take your spending and subtract your yearly basis withdrawal and you get the minimum income you might be able to realistically sustain over the long term.
Now, there are a few important thresholds for income where the ACA is concerned. From highest to lowest:
1) 400% of the poverty level ($48,560 for a single person in the 48 contiguous states in 2019). Above here, you get no premium subsidies.
2) 250% of the poverty level ($30,350 for a single person in the 48 contiguous states in 2019). Below here, you get some cost sharing subsidies that reduce the deductibles and coinsurance on silver plans.
3) 200% of the poverty level ($24,280 for a single person in the 48 contiguous states in 2019). Below here is where the cost sharing subsidies really start to look lucrative. A normal silver plan covers 70% of its customers' aggregate medical costs. Between 200%-250% of the poverty level, the silver plan covers 73%: a little better than normal, but not a huge difference. Between 150%-200%, the silver plan covers 87%, and below 150% they cover 94%. These latter two are essentially a platinum plan for the price of a silver!
4) 138% of the poverty level ($16,753 for a single person in the 48 contiguous states in 2019). Below here, if you live in a state that expanded Medicaid, you'll be on Medicaid instead of a private ACA plan. Pros of this: no out-of-pocket costs whatsoever. Cons: potentially lower availability of doctors depending on where you live and how many doctors take Medicaid patients.
Try to figure out which threshold makes the most sense to try for given the minimum sustainable income you calculated earlier. If that income amount is just a bit higher than one of these thresholds you can cash in on a slightly unsustainable amount of your tax-free withdrawal space and see how long you can make that last. Trying to go too far below is somewhat dangerous because once you run out of your basis you'll be stuck with income basically equal to your spending for the foreseeable future.
Again, sorry for your loss and good luck with the future.
* Once you turn 59½, your Roth earnings will become freely withdrawable as well. Otherwise any amount you add to this bucket will generally come at the expense of some other income (capital gains, Roth conversions, wages) in a prior year.