Ginseng root ficus, like I suspected. And it is the same as our local store here.
So, these particular trees are very common, sold exactly the way you bout it: cheap and easy bonsai for the folks who have only ever done regular houseplants before. It's actually two entirely different species of ficus grafted to each other. The big roots make it as hardy as a cactus almost, and they don't grow super large or fast like mother nature's ficus species will. Makes it easy to take care of in a small space, but you lose our on allot of the real bonsai aesthetics.
Like
@Carol 83 said, it's not real live moss as such. It's colored decorative stuff, and not needed. Take it off and and I bet you'll find run of the mill potting soil. That's not a bad thing per se, but if you dig around on the forum here - go nuts with that search function in the top right corner - you'll see that soil composition can play a big roll, and that many folks get very energetic about their discussions on the topic. Most have completely done away with all organic substrate components in favor of a 100% mineral mix with nutrients provided entirely by fertilizing. It's practically hydroponics at that point.
Curtains open is better, of course, but outside is best for trees. So long as there's no heater/radiator under the window to cook it, or really nasty drafts on cold days, window is fine for the most part.
Otherwise, doesn't seem you've made any major mistakes yet. Humidifier isn't strictly necessary. Ficus of any species are tough trees, adaptable to a great many environments that would kill other trees outright, and these ginseng ficus doubly so. They don't look like much, but it's hard to kill them if you have even half a clue.