The fact that the drivers are "bundled with OSX" is exactly the problem. Somehow mine are not working with PG, and never have on this one Mac. Because of some software that is "stuck" with OSX 10.11, I can't just upgrade the OS. I've tried everything short of a total backup/format/new OS install/recover data to fix this. If the drivers could be reinstalled SEPARATELY, that would be the first thing I'd try, but I can't locate them anywhere online. Obviously if there was a place, they'd have to have a set for every variation of Mac OSX, and nobody wants to go to that much trouble for the .00001% case like mine.
AP27 and GFN are the only apps (from PG) that crash it, PPS-SV works fine. Collatz crashes. SETI/Einstein/Milky Way/Enigma, all fine. I'm following up on some debug tracing advice shortly, should get better error diagnostics to work with. Only utility I can find is "OpenGL Extensions Viewer" which reports everything is working fine, really does have 3GB, runs all benchmarks. No clue yet.