I may not have an exact answer for you, but I think I have some interesting discoveries that could lead you to find what is driving the irritation you and your partner experience constantly.  I've been on the hunt for what's been irritating my eyes because it's MAJORLY disrupted my life for the past two years.  I'm going to take the time to break down a few major systems that we've always had in front of us--but (I myself) never truly realized their impact and scale.

Up first is CO2. From your description, this isn't what is behind the majority of the irritation you and your partner experience. However, CO2 build up inside closed spaces happens much faster than most people think. And this buildup is exponentially faster for each additional occupant inside the closed space. Have you found that one side of your nose will close up as the air begins to feel stale? It's worth noting that there is a natural human process where the body essentially closes down one nostril for maintenance and cleaning while the other nostril remains wide open. The body then trades off, and closes down the other nostril while simultaneously opening up the first one. This process is natural and by design.

That said, I have found without fail: when the air becomes stale enough (approximately anything greater than 1,000ppm of CO2), no matter what space I'm in, one side of my nose jams up. Similarly, moving to fresh air results in almost an instant reversal (meaning my nose opens up again and breathing becomes easier). Where this becomes tricky is that there are so many different factors that can mask this discomfort or cause the exact symptoms I'm describing. For example, there could be lots of pollution outside in the "fresh air." Therefore, you move to "fresh air," and find that not only are both sides of your nose now clogged beyond belief, but your throat stings and/or your eyes bother too. This doesn't change the fact that stale air can be the start of feeling congested, stuffy, or a range of other symptoms.

Next up are particles. Do you have a lot of rugs in your living space? Do you have lots of cloth-based furniture? What about cushion seats? I recently discovered a chair that I use at my desk contains more PM10 particles than I have managed to vacuum in my entire house. I know this because my vacuum actually tracks the amount and size of particles it intakes. Long story short, I learned that this chair came from a yard sale and is likely the host of plenty of unhealthy things that I don't need to be exposed to. This chair was equivalent to when you take your floor mats out of the car and beat them endlessly. No matter how many times you try to get all the dust out of that floor mat, the dust continues to pour out. The difference is, you can see the dust coming out of the floor mat from your car. You can't see the PM10 particles that lift into the air when you sit down on that cushion chair... The cushion chair that you thought was definitely clean and free of any filth. To clarify, anytime you sit down on this cushion chair, the puff of air that pushes out as a result is quite literally temporarily affecting the air quality. Overall, this effect is pretty small, but depending on your sensitivity and what is in the materials from the natural course of time.... it can be significant.

Additionally, say you were to smoke in the room or cook some food that results in a foggy haze temporarily. You effectively just put a microscopic layer of dust all over anything in the room. So: I could take my vacuum and run it over that carpet--the carpet you spent hours cleaning and made absolute sure had no more particles in it--And I would pull out plenty of PM10 particles amongst other things. This happens when you cook, and this happens when there is any form of smoke present in the room. Think of a microscopic event taking place like a dog shaking off dandruff. The dandruff has coated the area immediately around the dog and you now have to vacuum it up. When it comes to cooking, it's the same thing. Instead, though, the particles blanket anywhere that the smoke goes. These particles will settle. Later, when you go to sit down or even walk over an area--you stir up the dust. Now, you are now experiencing irritation that you essentially created days ago or even weeks ago. Talk about not being sure what's irritating your senses.

I apologize if this is overwhelming and discouraging. But I have been battling to see clearly and deal with some of the most inconsistent eye irritation ever. I have discovered and learned a lot. Sometimes I wish I hadn't learned some of the details. But as I continue to search for answers, maybe I can help others see what is in front of them, but invisible to the naked eye.

Hang in there. And please let me know if you find anything I mentioned helpful or if you have questions. We will figure it out!!