I've read conflicting articles about dust allergies. Some say air purifiers are helpful and others say they're not because dust is too heavy and falls to the ground. Should I bother getting one?
Well, if that's the ONLY effort you make at cleanliness, the filter won't be enough. However, it does sound like you're making other efforts, so the filter can be a good part of that.
Here's a plan for you. Clean the house, vacuum, etc while wearing a mask. (Or have someone else do it if you can afford to.) Leave the filter on and go out for a couple hours. Come back to all the dust either in the filter or in the garbage!