Thank you Peter for this nice summary!
Regarding the sky-flats, dithering can help there but then I would say you need a bit more frames to get proper rejection for the rejection algorithms, usually this amounts to 15-20 frames. I'll try again with some better rejection parameters.
Regarding the light fall-off; good point indeed, however I would then say to stay at max 70% or so, I'd rather have some small issues in the corners which I can crop, then in the overall image. In this case I got a bit over over-correction in the corners, no change in the overall image (as it's clean already) and an added white stripe.
The light on the sensor for the darks is also an issue as when used, it gives massive over correction in the integrated image. I really couldn't use it.
Thanks a lot for the trouble! Vincent