Hello,
I have the same problem (the same set of errors) on Unity 2019.3.0f6 and Wwise 2019.2, both on Mojave and Catalina (different machines).
What I can add to this is that my project stopped working after I've tried to reimport all the assets. The very same branch, but without Library/Temp/obj folders already built does not work.
So it looks like it's not a matter of codebase, but rather what's Unity doing while importing/caching assets.
I'm investigating this, because it blocks my project. I've tried deducing what's going on, removing things, but it only started working (i.e. assets import, without "too many open files" crash) when I removed Assets/Wwise.
So I believe it depends on what's inside Wwise project and whether all the assets are already imported.
I'll let you know when I figure out more.