Can you share your FIT file?
Also, regarding the images you linked. Both are from vdb, however you have to understand that the QSI image was made from a total of 17 hours of data in total, while the QHY was made from a mere 2h31m30s of data in total. While these modern CMOS cameras have very low noise, you still need to get the necessary integration time to get a good result. Vdb's QSI image has SEVENTEEN HOURS of integration! That is almost five times as much as you currently have.
I think it's probably mostly just that A) you are fighting a lot of LP which is adding a ton of noise, B) you are imaging with a relatively slow scope and C) you only have 3h27m of integration with that combination of detracting factors, when you likely need three to five times that.
Imaging in LP is rough, and the main reason I primarily do NB from my back yard rather than LRGB. It just isn't worth the required time investment to do LRGB from my deep red zone/white zone back yard. I, too, need umpteen gazillion hours of integration to really get the best results...and that has been true with every camera I've ever used. Conversely, if I hit up a dark site, I can get in 2-3 hours what it would take 30 hours or more from my back yard. LP is an AP killer.