Hmm, never came across those kind of problems. I’ve played and completed KQ6 in DOSBOX. The game ran perfectly… Sorry 
Don’t have my old laptop anymore, but I’ve created a dual boot with Win95 on my computer so that I can play all those great games that won’t run on XP or DOSBOX. Maybe you should consider creating a dual boot? Worked for me!
Anyway… Here are couple of Sierra links that might help:
http://www.geocities.com/TimesSquare/Arcade/7435/Goodies/Downloads.htm = Quest for Glory game patches.
http://www.geocities.com/belzorash/ = other Sierra game patches.
http://www.adventuregamers.com/forums/showthread.php?t=9339&page=2 = Link to running KQ6 in DOS. Scroll down a little bit, there you will find a resource.cfg file that might work for you!
Good luck!