I've even played some piano where you have to read two lots of music and the notes are not quite the same on each. It's one of those things that you just have to work on and I don't do it enough to be fluent. I struggle a bit on reading rhythms. Of course if I hear the tune first then it's not so bad. Complicated music will be hard to play anyway.
For stuff I do with the band I mostly just have chord charts and I simplify some of the complex chords.
Yeah, I can work with a chord chart and I am pretty good at improvising. As long as it isn't something crazy.
I am in awe of you my fine music reading sophisticate!
I try to keep up with my theory knowledge but sadly not the notation part!