To your questions. 1) Finra issued an information notice in 2019 covering this topic. https://www.finra.org/rules-guidance/notices/information-notice-051019 2) The $2.50/share is a margin maintenance requirement placed on the entity shorting the shares. No money changes hands for this. There is no favorable treatment. 3,4) MM are permitted to make a market in a stock to provide liquidity. They can move the intraday price but only with a coparty to buy or sell. They normally do not carry their own inventory but buy/sell per their customer orders.