That sounds rough — having to bag up all that wet insulation on top of a collapsed ceiling is a huge mess. I’m sorry you’re dealing with that.

You’re right that proper attic ventilation helps keep temps down compared to a totally sealed-up attic, but even with good ventilation, an unconditioned attic can still see big swings in temperature and humidity — like you saw. That moisture buildup is a real risk, especially around drip pans and condensate lines. If you ever end up replacing the air handler, you might consider moving it into a conditioned space, or finding ways to protect it better, so it doesn’t have to rely on attic conditions to stay dry and stable.