I'm in the business myself (side job). I don't like the sound of this situation.
There *is* no "normal", let alone a "new normal". There is, in most places, something you might call "typical", and there's what you agree on.
In my state, it is illegal to establish a market rate for commission, or to tell a customer or client that there is a going rate. We typically charge a total of 5-6%, but that is set by mutual agreement between client and agent, and I have never been pressed by my broker to charge more.
While it is legal for a brokerage to encourage higher commissions, it is greedy and shortsighted, and I would not appreciate it as an agent or as a client. If they're not making enough money, they should focus on improving customer service, not charging more for the same old shit.
You say you're uncomfortable with walking away because of the time invested to date, even though you legally could; I suggest you directly state your concerns over this bait-and-switch, emphasizing the importance of expectation management and keeping to your original agreement. Something like, "I've thought about this, and I understand that you're under pressure to increase your rate. For this transaction, since I've been working in good faith based on an informal agreement, I am not comfortable with increasing the rate after the fact. I would be happy to proceed based on our initial agreement and hope you agree this is both fair and worthwhile."
See what they say. In most markets, competent agents are easy to find and easy to replace (it's happened to me when I didn't meet expectations), and getting the agreed-upon commission for a job should be more than enough to satisfy them.