Glad to hear you have it tamed down to your personal preference. It's a shame having to leave out the fill screw though. When everything rolls together just right, it can be left in without any change in wicking.
A few things to try or check for that might help improve the wicking:
Is the wick end inside the tank cut at a 45% angle? (cut and then retorched to dissolve any frayed ends).
Did you use a straightened out paperclip to use as a rolling tool inside the wick? Using a tool like this, helps to assure a good solid air hole through the middle.
Perhaps the wick has too many layers and is rolled too tightly? Perhaps the opposite? Perhaps there's not enough rolls?
The coils are snug but not tight and choking the juice flow right? Can you gently lift and twist the wick out of the coils and reinsert?
It's usually one little thing... one tiny little thing that can be so exasperating. Best of luck, and don't give up! You'll soon have it all, the wicking, the flavor and the no spill/leaking

Honest!