I'm really curious about the small structures in his lungs. I would have feared them getting totally trashed by the pressure imbalance, making his lungs useless even after the outside pressure was restored.

Vacuum is good insulator.

Initially he would probably feel warm in the in vacuum.

The evaporation of water would cool his mouth and nose.

About twenty years ago, I knew a guy who owned a snake that was fed with live white mice. Once, around feeding time, he and another guy we knew ended up making a bet about what would happen if the mouse was exposed to vacuum prior to becoming lunch. Long story short, it was put in a glass chamber from which the air was evacuated over the course of about a minute. Basically, it sniffed around for a few seconds then abruptly fell over dead, with the only external sign of damage being a small dot of blood on its nose.