They're fine. Try to clean them up with some sand paper. You can use some 1211 or Yamabond when installing that seal to close up any gaps there may be.
Swap out the 3 OEM springs for the 3 stiffer ones and see if that makes a difference. If not, you probably need a new clutch and all 6 stiff springs from the start.
17.5” shock length, but what’s important is the reservoir length. There’s a 5” and 3.5”. You want the shorter so it doesn’t hit the upper arm during compression. I have a race gas 4mm Serval making 100hp.
Main jet gets clogged? You have a screen in your tank? You’re obviously getting debris into the tank, otherwise your carbs wouldn’t be getting plugged up.