Yes... the last point is a valid one and I am not very comfortable with it.
Amazon blacklists sellers if they sell their products at a lower rate in any of the other online platforms. If the California authorities want to eradicate this practice, then I am 100% in support of them. But given the socialist/communist leaning of the current California representatives, I really don't think that their intention is that good.
Here in India, it is an entirely different story. Offline stores (who used to overcharge the customers by up to 2x) are mad that products are being available at very cheap rates in Amazon.
Similar to that, a cut for Amazon from the seller higher than the other is a normal thing in online distribution or retail. About how one popular distributor demands more cuts than the less popular ones. Steam, for example, takes 30% share from the sales on there. Epic Games, another platform to sell games only take 12% from the sales, the rest toward the devs. All are fair in the open and competitive market.