This is by no means a definitive guide to curing, only the methods I've used since I began growing.

1) I always end drying and begin manicuring when the stems feel fairly brittle, or snap in half between my thumb and forefinger. And you don't need a fan inside your closet, but you should try to keep air circulating NEAR the closet as much as possible. Maybe keeping a fan positioned in the room to blow on a barely opened closet door? Either way, you don't want the air inside the closet to be stagnant for most of the day.

2) After manicuring, into the air-tight jars they go! And, I probably break all sorts of curing guidelines here, but I like to slightly compress each bud with my fingers before placing them in the jar. I've just noticed that they seem to remain a little denser when finally dried, but you will end up removing a fair amount of trichomes from the outer buds this way. Not a bad method of making finger hash, though. (Probably shouldn't do this if it's not a very resin-laden bud...as it would take away some amount of potency. But if it's covered in frosty trich's, the effects will be less noticeable.)

2a) I like to keep my "sample" buds separate from the other buds that'll be slow cured, so that I can water or heat cure them all at once.

2b) One month is the minimum amount of time that I let them cure. If I'm not in desperate need of replenishing my stash, I'll keep them in there a bit longer. The longer the cure, the better the taste and aroma of the end-product.

3-3c) If I have any amount that I want to store for any extended period of time, I will generally just use a thick Ziplock (or similar) bag, and vacuum seal it. The buds are going to compress quite a bit, but as long as they didn't dry out too fast, they'll fluff right back up as soon as the bag is opened again. I don't keep anything in the freezer, because I plan on consuming it within a fairly short amount of time...but if I were wanting to preserve a batch for months to a year for whatever reason, I'd probably keep in a freezer. Otherwise, I keep the bags in the bottom drawer of my nightstand, where no light can touch it...and temperatures aren't high.

I suppose the Tupperware idea is feasible, but would probably be a bit more difficult to vacuum seal. If there's excess moisture inside the container, and you end up freezing it, it can probably do some damage to the cells of the buds...possibly affecting potency. Not 100% about this, but it seems fairly logical. Perhaps this is where a desiccant agent would be useful?

Again, since I do not freeze my buds or add any agents containing Vitamin C, I have no advice to offer about length of time between thawing and consuming, antioxidants, or preservatives. But I'm sure someone will read this who does freeze their buds, and they'd probably be more than willing to share their methods with you.

Hope that at least answers some of your questions.