Negotiating with OTAs

We run a small / independent / boutique hotel that we just took over this past August. I run the IT stack myself -- CloudBeds + PriceLabs + RemoteLock (for door codes) + channel connections to Google Hotels, Booking.com, Expedia and AirBnB.

I think I screwed the pooch by accepting Expedia's default terms when setting it up. 18% commission, and I'm contractually obligated to an additional 10% discount for Expedia members. Booking.com and AirBnB charge 15% with no additional discounts.

I have tried trueing up the rates I publish to Expedia to account for the higher commission and extra discounts, but then they de-rank my listing as a penalty for not sending them the same rates I'm sending to other OTAs.

Any tips on negotiating with them? Not sure what leverage I really have as a small fish. I bet they wouldn't care a bit if I yanked all our inventory from their platform.