No useful vision accessibility options

That's not good. Although I haven't tried them, here is a link (below) to information on accessibility options for the Quest, including visual impairment. Not sure if helps but good luck. It might have been a good idea to go to a store and try out a demo model to see if it suits your needs. As for leaning in to get closer to a window, it can go grey if you are moving outside of the set boundary. 

https://www.meta.com/en-gb/help/quest/674999931400954/

Firstly, the font size is very small and the font size options seem to do next to nothing. I can't see much difference between regular and largest text. Why would there be all these text size options if they do nothing?

You need to restart the headset after making the change. It seems to mainly increase the font size on the menu bar and in the settings menus. There's a text-to-speech option under "Vision" in the menu, and a "screen reader" setting under "Experimental".

There's no zoom feature. Mainly, you need to move closer to objects, virtually, or physically, but in the user interface, when you move windows closer or further away, they have this (sometimes useful, sometimes annoying) habit of automatically resizing themselves.

It's not possible to disable the greying-out feature when you pull windows in close. Maybe the new Navigator interface will be different, but few users have access to it, and after many months of waiting, it still hasn't been rolled out to the majority of users.