Keeps 4 days refrigerated and freezes 3 months, but freeze it without the noodles — they disintegrate. Add fresh noodles when reheating; they take 6 minutes.
Under-salted, or not enough aromatics. Sweat the onion, carrot and celery properly first — 5 minutes of real softening builds a base that chicken and water alone won't.
Yes, and it's a good shortcut. Add the shredded meat in the last 5 minutes so it doesn't overcook, and use a good broth since you're not building flavour from raw chicken.
There's modest evidence that steam and warm fluid ease congestion, and the hydration helps. It won't shorten the illness, but it isn't purely folklore either.