That's a scary story. So glad your alarm worked and woke you.
I'm a big advocate of sleeping with a window open. I was just camping at -13F with a wind chill on top of that and I slept with a window a 1/4 way open. I try to open the passenger side window to lessen the chance of CO gas from the furnace entering the camper.
I'm not a big fan of opening the turn buckle doors when sleeping as I hate the thought of a mouse getting in. I just had one crawl up me on the trip I was just on. I was eating chips and watching Netflix in a cook house with a stove. Things were pretty cozy until the mouse crawled up onto my t-shirt. It freaked me out. I woke up that night freaked out and it's been on my mind a few times since then. So gross.
I learned the hard way not to leave the access panels open when one night I had a squirrel come eat my food and sleep with me on the couch.