All seems above-board to me.
1) Airbnb collects occupancy taxes for some states and countries, and not for others. If taxes are not being collected and remitted by Airbnb, there is a way to add them using a host tools add-on. I do this for one of my properties. I see no problem with this, and you do owe occupancy taxes, just like in a hotel. Check the jurisdiction (or just check a hotel in the area) to see if the correct occupancy tax is being charged. Instant Book vs. booking request should have nothing to do with this, it might just be an awkward sentence.
Here is a (hopefully up-to-date) list of taxes that Airbnb collects and remits directly to respective governments. Note that there might be additional local taxes that the host needs to collect separately.
https://www.airbnb.com/help/article/2509/in-what-areas-is-occupancy-tax-collection-and-remittance-by...
2) A $400 cleaning fee seems reasonable if the place is big, beautiful, and expensive as you say, especially in these “new normal” days of Covid where extra disinfecting is required. It also depends on the locale. If you think it seems excessive, you can compare with similar properties on Airbnb in your locale and price range.
3) The Airbnb fee is what it is. Everyone pays 10-15%. No discrimination there.
4) I approve of a separate rental agreement being signed. What guests can do and have done to Airbnb properties is truly shocking. A rental agreement shows a very diligent host who loves and cares about his/her property. If the terms in the rental agreement seem reasonable, don’t take it personally. If not...perhaps a property with looser rules would make you feel more comfortable.
To a certain extent, host/guest relationships are built on trust from both ends; On the host’s end to be truthful about what they provide and what the guest should expect, and on the guest’s end to respect the property and abide by House Rules. IMO, you shouldn’t book this property if you are not feeling the trust.