D. Aggregatum questions- winter rest and others

[Fishkeeper]

I found a D. Aggregatum at Lowe's today, and, after some quick Googling on my phone, decided to give it a try. So, I'm here with questions.

First off, how do I tell if it's getting enough light?

Second, it has a grower's tag with it that says:
21656 Dendrobium
Aggregatum- Thailand
Specie- 11/13/12
I assume this is an ID code, the origin of the variety, and the date it was planted. Am I correct?

Third, and most important, I've been reading about the winter rest that they require, where you just about stop watering the plant. If I don't do that, will the plant die, or will it just not get the signal to flower?

And are there any other tips?

EDIT:
Additional question. I've just gently de-potted it to take a look, and it's not terribly happy at the moment. I couldn't see the roots because of how it was packaged, so I went by leaf health, which is great. The rest of the plant is a bit unhappy.

There are at least a dozen pseudobulbs, ranging from 1" to 1/3" tall, and they all have leaves that appear healthy. However, the pseudobulbs are badly shriveled, so badly that they're ridged.
I haven't cleaned the root ball off to check on all the roots, but some are kind of dull brown and haven't greened up in water. The plant appears to have some good, healthy roots, though, I think it just hasn't been watered enough. Or, possibly, the usual "spray all the orchids with the hose" treatment just wasn't enough water at the time because of how it's potted.

The substrate is mostly charcoal and perlite with some big chunks of fir bark, which I think is a fine substrate for this type of orchid, but it probably just couldn't hold enough water from the spraying everything usually gets.

I want to get this plant re-hydrated, but I'm not sure how to do that safely- any advice? I've poured water through the pot a few times to help moisten everything up, and I'm leaving the pot soaking in water for about 20 minutes. I assume this will put as much water into the bark as the bark can hold, which seems like a good thing at the moment.

How long should it take, with regular watering, for the pseudobulbs to plump back up and be healthy? Should I water more often while re-hydrating the plant?

Also, could I grow this plant in pure charcoal and pumice? I'm working on a setup, a miniature living wall, that I want to contain as little organic substrate as possible to help prevent fungus gnats.