I hadn't thought of that at all.
I tried -current, that broke the machine rather violently :) ended up in a db{6}: prompt without any USB support. After a bit of fiddling around, I realized that starting over would probably be the fastest way of going. It is now happily chomping away, with a lot less load on the system overall. Without --disable-threads it would ever so often spike all 8 Cores, and it wasn't uncommon for it to have a load >2.0 - now it is sitting comfortably around 0.32. And it doesn't seem to have any impact on the system.
I still see
3417 named 43 0 713M 503M parked/5 3:34 19.82% 19.82% named
Where I guess the /<number> means what CPU/Core it is currently parked at, I see them often enough to think "What?", system runs smoothly though. Then again, it has "only" run for 30 mins, but that is 10x longer than it could before.
Thank you all for the great and fast help :)