None of the brokers wanted to go commission-free. IB might need to in order to stay competitive. Or maybe not, not sure. I like their API, but I don't actually need it. I use it to pull historical data when the market is closed rather than execute trades. I could use a 3rd party source. Where IB blows TD out of the water is on their cash sweep interest rates. TD basically pays nothing. All I'm basically giving up so far by staying with IB is their zero commission stock and ETF trades. I don't think I would save that much on options / futures commissions with TD over IB. https://www.tdameritrade.com/pricing/margin-and-interest-rates.page
Nope. They make more by charging commissions rather than selling order flow. Otherwise, they never would made IBKR Lite -- they would have just added a commission-free order routing option and made that the default.
There is a lot here and I want my response to be general and not targeting why any particular broker does anything, as I do not want to speak for them. PFOF for opening and closing orders, if those orders are sent to the primary exchange to be part of the opening and closing auction, is not something I'm aware of. If that is true, not only will the NYSE/NASDAQ charge a fee per share for that execution, but your broker will have no offset to cover the cost. And, when you send your order to a MM that pays the broker, e.g. VIRTU and Citidel, they want what they call "dumb" order flow not what they refer to as "toxic" order flow. They love small market and limit orders. The market orders, they can trade against in their portfolio and the limit orders that are not marketable at the time of execution provide them a credit when executed. What is toxic to them? Large market orders in illiquid stocks. Orders that always arrive just before a price change. I'm sure there are more, but those stick out as orders they can't make money on in the short run. They do not care what the stock does in the next month, only in the next few minutes or seconds. We, Lightspeed, we asked by these routes years ago to take those routes off our DMA software. We were asked that also at the broker I worked for before Lightspeed too. They don't want scalpers laying off positions before a price change and momentum traders playing breakouts. They want investors and swing trading flow. I hope this helps.