where pet-g is concerned, try and keep your temps around 220-235. layer adhesion is apparently much better at the lower end of the printing temperature.
IT also prints slower than pla and up the bed temp to around 60-70c

On the retraction settings - too much and too slow. 6mm is a lot of filament to keep moving. 2-3 works much better. Simplify3d default is 1.8mm and all I've ever used on my flashforge.

Retraction speed should be as fast as your machine can comfortably handle. I've found 60-70mm/s to work for mine. A retraction should be a short fast action. I tend to use a lot of retraction (moving, layer changing etc) I generally get no noticeable stringing. A small length retracted quickly works better than a long length done slowly.