Help: Luke 3 HH – Setup problem

lately I’ve been having some major issues with uneven action on my Luke 3.
On the upper frets (1-9) there is fret buzz, but at the same time on the remaining frets the action is way to high.

I use 10-46 strings instead of the factory 9-set and I’ve made the necessary bridge and spring-adjustments for the bridge to float nicely.

I tried to adjust the trussrod, but honestly the neck sits pretty good already and it didn’t really help with the “unevenness” of the action. Ive also tried to temporarily downsize to a Hybrid-set to make it slightly easier to play, but it really didn’t do much of a difference.

My hypothesis is that a bridge-lowering is necessary, but i’m totally clueless on what measurements to aim for and frankly I’m too scared to do it without proper guidence.

There really isn’t any guitar-tech nearby either, so i’m pretty much bound to do it myself.

If anyone has any tips/tricks, please share! Thanks!