We do nr 2 (we have a store for nr 1 + sort of blinders), we got the temp at only 28-29°C.

Outside:

That's the thing I can't get my german roommates to understand they keep opening the windows in common areas when it's the peak heat of the day.

Sorry guys lüften can't fix everything

I'm in the attic so all heat goes to my room; I need to keep the shades down 95% but leave the window open so the heat can escape and air can circulate.

For 1 these metallized emergency blankets work much better. Aluminum foil also works but it's not as durable when put outside

Yes, this exactly! This works especially well if you have temperature sensors in your house, since then you can know when exactly to open and close based on the difference between internal and external temperatures (or at least that's what I say to myself to justify my Home Assistant setup). Extra effective if you put a fan in the window during the cooler night.