There are different yeasts in there; 3 if memory serves. I've propagated it a few times and used it in a beer once. It was very good.
To answer your first question, make a larger starter then smell the starter. You should get a nose like DT. It is not a lot like any other beer, imo, so you'll probably know what it is straight off. Other than that, you'll have to make at least some beer to be sure and, even then, you'll never be 100% sure without lab testing!
To answer the second question, to my knowledge, DT uses the same yeasts and does not filter out any one strain during bottling. They do have a pretty long fermentation cycle, though.
What I may have done, rather than putting an airlock on the flask, I would have used sanitized foil or the like. Starters / harvested yeast tends to need plenty of air to breath. But, if it is currently foaming, I'd say you're OK. Just keep bumping up the starter size and you should be good to make a beer!
Hope that helps and good luck!