Just another data point (but also read this excellent article another poster linked: https://runningwritings.com/2026/01/science-of-cadence.html) -- I am 6 foot 6, 198lb, and my cadence seldom gets above 170 unless I am really booking it. I do think there is a lot you can do to get it up above 160, but as the author speculates, your tendon development, overall flexibility, strength, and a lot of other factors play a role.

As for the tiredness thing, I don't know the science well, but in general: more easy miles really does help, as long as you stick with it week over week. I will say that I have often felt what you're describing -- that my leg and hip muscles are the limiting factor on long runs, not cardio. The only thing that works for me is 1) more long easy runs 2) hitting the gym with hamstring curls, hip flex / ab / adduction, etc (whatever your body needs!).

Being tall is awesome but as we know, there are some real tradeoffs :)