Hi @patrick,
I too am blind, and am interested in the possibility of composing for video games.
It looks like Andy didn’t respond to your questions.
I’ll attempt some responses to give you a better understanding of how we go about using screen readers.
The first rule is that we should be considered keyboard ninjas. That is to say that any implementation of keyboard commands, shortcuts ETC. is very much appreciated.
though we do have some control over the mouse pointer with our screen readers, it is rudimentary at best, and quite frustrating when we have to rely on it.
When working in reaper we use a deeply integrated extension called OSARA. https://osara.reaperaccessibility.com/
though it was not developed by Cockos, it is fully supported and the OSARA devs have high level contact with Cockos.
OSARA makes extensive use of the keyboard shortcuts facilities in Reaper, as well as the SWS extension.
We navigate the interface using keystrokes and keyboard shortcuts, as well as menu diving. OSARA provides spoken feedback by passing info from Reaper to our screen readers.
When working with the timeline, for example, I select my track by arrowing up and down until I hear the one I need spoken by my screen reader. then, Assuming there is something on the track, I press ctrl/right arrow to select the item I need to interact with. If I want to move it, I press ctrl/x, I press ctrl/j to jump to a point on the timeline, and ctrl/v to paste my item.
If I need to split the item, I either play until I get to the split point, or scrub by tapping right/left arrows to find the place I need. I press “s” to split.
Almost every operation is available via a shortcut or menu item, and when feedback is needed OSARA is able to pass the feedback on to the screen reader. About the only thing I can’t do is look at a spectragram or routing diagram.
For adjusting values in plugins and the like we rely on midi implementation in the plugins. If a parameter is exposed to be controlled via midi, then OSARA has a parameters dialog where we can tweak thee parameter through use of direct entry of values or moving sliders up and down with arrows or pgup/pgdn.
When midi implementation is not provided for a parameter or control, sometimes we are able to get by with an OCR solution which allows to click on the screen with mouse commands. This isn’t ideal though.
I hope this is helpful.
As a starting point for accessibility i would suggest that you implement as much keyboard control as possible.
I’m just learning about the existence and use of middlewear but I hope that when I’m ready, that I can take advantage of FMOD to create some amazing game scores.
Thanks for reading! 
Rusty