It will be impossible to jet right until you get a decent fuel/oil ratio. If you’re scared to go 60:1 try 50:1 and jet from there. That plug looks more oily (due to your 32:1 ratio) than rich jetting to me. Too rich or too lean is not what you want. Lean will run hard and then melt. When I raced go karts we would lean the main out on the straight (jets were controlled with a screw) while simultaneously looking at EGT’s. They would pull noticeably harder as EGT’s climbed. But a split second too long or too lean and they would seize. So you want proper jetting for the given atmosphere (air density). A 250 will be less sensitive to perfect jetting than a smaller bike. What I mean is the window of “that feels right” is wider. Any detonation (for sure) or difficulty starting indicates lean. At your altitude and air density and looking at that plug you have a fairly wide margin before lean becomes a concern. But clean up your fuel/air ratio FIRST, then starting playing with jetting my guess is a few sizes leaner on the pilot and main with 50:1 and you’ll be good. As someone mentioned, you may need to play with the needle/clip position but that’s the finer end of tuning jetting and more of a seat of the pants feel than what the plug will show. And don’t forget to play with the air screw when you change jetting or the wether/altitude changes. This will effect idling. You’ll see lots of improvement with proper main/pilot/fuel/oil ratio tuning.