I'm not really a ficus person but I am almost positive the east window thing is good. But if it's too sunny out, then the window might have a chance of magnifying the sun's rays and do damage to the leaves. I remember reading something that you should place your tree about a meter/yard away from your window because of the temp. difference. There could be a draft, the coolness from outside has an effect on the air inside as well. I would place it about a meter away. As for watering, ficus isn't my ball of wax so I would a bit for more info on that. Mossy surface is a good thing. Just make sure it doesn't cover more than a quarter of the surface of the pot otherwise it could effect watering and such. I wouldn't mist it more than 2-3 times a day. If that.
Wait for more folks to come around and give advice.
~ Ken ~