You need a repair/ maintenance manual. They are copyrighted and this site does not condone asking for illegal copies. So look to get a used manual here or on e-bay.
You need the manual to do the valve check. Whilst at it change the coolant since it's easier to work on the valves with the radiator removed.
Electrical gremlins: Whilst you have everything apart check all the accessible connectors for good contact (no burned or oxidized = brown/ black connectors). If all is clean, add dielectric grease to them and re-assemble.
Google here and read up on starter switch issues, headlight relay kit.
Not sure how the high beam comes on on it's own. Look for any aftermarket electrical additions, maybe some botched wiring job?
Check into a Booster Plug
, or look into a power commander to make the engine run better at low rpm's. Stock, the engine is probably happier above 3500, especially with heavier throttle input.