you already deleted them and that is fine.
Quark caches the fonts and postscript files it generates (if you use Quarks internal PDF making capabilities)... I don't know the exact purpose of the JAWS folder but if you turn on the full res preview option, it will dump it there too.
I have 2,200 TTF instance JAWS files . . . WTF Quark??!?!?!
Feel free to trash everything in that folder but be aware that once you do you might have a small delay depending on the systems hardware as Quark recreates the files it needs on the fly.
oh - and that second burning question - NO you can't turn it off.