Thanks! I DID run without plugins and stripped down whatever I could, running a generic template file (then that file was added to my files that reload each time!)
I would guess this is related to upgrading to High Sierra but it didn't happen until 2 weeks after that. So I decided, heck, finish the job and go to Mojave OS. Then that didn't help so I went to SU 2019. And after hanging on the first try, that looks pretty good. Now despite some crashes, 2016 closes OK... sometimes... after all that, what, can it heal itself???
After 3 years (versions) I have to say there ARE some nice changes piled up that look good for the Mac. AA is good now, it does seem a little snappier and smoother, and crashed files will not be loaded on restart supposedly. And they made it for Mojave. I like that they finally made the extensions manager into a sensible dialog window-- though after loading Sketchucation Tools I don't look at it much again.