The point of this exercise is to find a position where there is no net force pushing the pick in either direction. With this pick orientation the upstrokes and downstrokes will sound even, and both should feel smooth. You posted a video earlier in this thread of a fantastic tremolo, but also commented that it felt like the pick got stuck. To me it also sounds like one of the pickstrokes is louder than the other.
Is there a different grip you can try, that lets the pick move even further in the direction “it wants to go”? Perhaps one of the trigger grips?