If you are getting no vapor but the herb is extracted, it sounds like you have an air gap in your vapor path... at 390 you should be able to get lung busters if you want them. So check your seals with the cooling stem?
Also not sure what you mean, the standard long thin stem does not need the cooling unit kit, it slides right in on its own...? My FW7 came with the standard long thin stem installed in the new style mouthpiece, and the pieces for use with cooling stems...
Contact Marc if it seems you are missing any pieces! He can also help if there are any performance issues, anything at all!
Fine grind is good, but it does not need to be super fine, but what you want is a consistent grind. Fluffy is not really the issue, you can still pack it down well enough. How much are you loading though,? You should try only loading half full at most to learn properly...
I can get great hits, riding the lowest setting it comes with by default, with long slow draw hits no matter how I grind really, though that does affect other aspects of the extraction.
Remember that even though there is automatic regulation, this is still a manual on demand vape, there are a lot of varying factors that can affect your experience.