For #2
I would stop changing things around. Leave stuff set at sensible/very conservative values for now.
So disk cache set to be large enough to fully cache a session (not “normal”).
IO buffer size set at 1024.
Do all usual optimization (do everything you can and leave them all done for now, get *all* networking turned off)
Make sure there is no other unnecessary software running.
And in addition to usual optimizations also disable tailspind and spindump.
https://avid.secure.force.com/pkb/ar...-Errors-on-Mac