Worn out sprag clutch? Sounds like it started skipping, and now not gripping at all.

There should be a steady flow, and it should be the same in "on" af "res" setting.
Did you disassemble the petcock entirely?

Blocked fuel = lean = high idle, so yeah.

I'd check the pilotjet for debris

Check the fuelvalve and the filters in it. Also make sure fuelline has no kinks, and no blocked fuelfilter.

Whats the deal, any bike would go way expensive when doing the same...

I have a H4 led aswell, you can buy adaptors on ebay ect to make them fit, so I took the easy route on that one. Love it at night compared to stock. I have led al the way around, but no blinkers installed.

Check the choke passageway in the floatbowl, for some reason people never clean this when they clean the carb.

I think the oil pump should be able to add sufficient oil, using a half-decent oil.
Many enduroriders on 300 2-strokes use way less than 3%