Now that you have the high speed jet adjusted, you should adjust the low speed jet. That is the screw with a spring underneath its head, that sticks out the top of the carburetor's body a bit to the left of the middle. You just set the speed control for minimum, and adjust the idle jet by finding the lean limit (it slows down and runs a bit erratically) and finding the rich limit (it slows down, sounds sluggish, and gets erratic in a different way). Then you set it halfway between the two limits.
You need information from the manual to deal with the cutting disk. They tend to have a sort of disk brake to keep them from spinning when they are declutched, so from what you have said there may be nothing wrong with it.
