"But if I were to sell, say, a large volume of STEEM in a hurry at the current highest bid, I would only be able to sell so much of it, thus forcing me to lower my price and drive the market down. Again, am I understanding this right?"
Exactly right. The more you sell, the more you would drop the price. Unfortunately, I'm not sure if it's possible to accurately model exactly how much selling pressure it takes to drop the price at any given time. I can compare the relative volatility to something like Apple stock, but only with the benefit of hindsight. I couldn't tell you at what point your personal slippage becomes material to your total income.
However, I can tell you it's about 66900x less than it would take if you were selling Apple stock, and I suspect it is actually very material to a lot of users. You absolutely cannot dump 6 figures or more without a material price change.
Thanks for taking the time to answer my question. Looking forward to the rest of the series.