the most important rule is:

if somebody else is wearing a mask, wear a mask around them. But everything else is true also

For 2, I make sure to air out the space by opening windows and/or usually having air purifiers, but otherwise I'm pretty much following the same guidelines as you. Though, as we travel deeper and deeper into The Forest of Are You Freaking Kidding ME I find my definition of crowd is getting smaller and smaller. Really, I just don't put myself into the situations where it's an issue as much. I put my mask on in the parking lot, if I wasn't wearing it already, because sometimes it's just easier to leave it on, and then I don't take it off until I'm back at the car/home. The occasional times I go to the homes of close friends, I only take my mask off outside and make sure I'm either directly under/in front of a fan or put some significant space between myself and the group; Sit back on a bench and hold court kind of thing. Probably the riskiest thing I do is bike drop off/pick up from school for the little ones where I'm putting my hopes on there being enough air flow to keep from catching anything as we ride past the crowd. Realistically, one snotnosed brat sneezing on me would be the start of a bad time though. Also, pets, I try to only unmask around them either outdoors or in a room with an air filter, but I'm probably putting too much faith in the species barrier given we do know they've been catching our pathogens. But if we go to that point I'd have to mask in my sleep.

edit: I should note, that being a bubble of 1 living with family, I do mask at home as well except for in my bedroom/bathroom where I have filters. I eat out on a porch where I have fan on. Which, of course, doesn't stop my family from coming out and having conversations with me as they sniffle away. So yeah, them and my cat/ their dog are the likeliest infection vectors.

Any time I’m outside, I’m masking. The only time it comes off for me is to eat lunch at work and I basically hide way in the back of an alley behind my building where people rarely go, which even that I don’t like doing but I have to eat. Aerosols can stay in the air for hours and travel far, plus I live/work in a city so there’s not really anywhere I can go where I know for certain someone wasn’t there recently.

The risk is lower outside because covid won't build up in the air, but you can still get sick if you walk into someones exhaled breathe. Covid hangs in the air similar to smoke. Risk goes up if you are in a crowd, if there is no wind/stagnant air, or if there is a covid wave in your area.

I've seen quite a few people report getting covid by just stepping outside to talk with the neighbors, or going to the store and putting on a mask at the entrance.

I've found the head strap masks more comfortable than the ones that loop around the ears for long term wear (I wear one 8hrs a day at work), and they are more effective, but all masks cut down risk.

BTW, we are currently at historic lows for covid, and it will probably stay that way for another few weeks. If you want to track the risk JPweiland has been pretty accurate in predicting covid waves and current risk, although different regions can vary wildly at times. https://xcancel.com/JPWeiland - https://bsky.app/profile/jpweiland.bsky.social

1. I don't mask up outside when there's very few encounters (measured in minutes between encounters rather than encounters per minute) and I can just cross the street or take a wide berth to avoid contact (in my case, this boils down to car-dependent suburbs or off-season hiking trails) but I mask everywhere else. Even then, I think I might have caught something because I walked a little too close to a group of kids and then had a 24-hour bout of chills and aches a few days later (never tested positive for COVID, thankfully, and I haven't noticed any sequelae). If I'm going on a walk with someone outside of my bubble, I honestly just mask. At first I would do the distance thing, but then I would constantly be worrying about it, whereas if I mask I can just be present.

2. If it's not a space that I know a lot about in terms of occupancy, filtration, and ventilation, I'll always mask. When I have people outside of my bubble over at my place, I'll do the best I can in terms of opening windows, running the A/C fan continuously, and running air purifiers. Once they depart, I leave that all in place while masking for as long as I can bear. I don't have a very scientific way of handling it, but it's always measured in hours. If someone has a good resource for making more informed decisions about this I'd be very interested!

3. Not much to say about this one—pretty cut and dry.