Your radio settings and mechanical set up are screwed up. Start with 100% travel volume in both directions and a pitch curve of 0%, 50%, 100%. Move the collective to exactly half stick and center the servo arm (use sub trim if necessary). Then adjust your pushrod lengths to (1) bring the swash to the center of its available travel, (2) make your mixing arms as close level as possible and (3) put the blades at 0 degrees pitch. Once this is achieved, go to full collevtive and measure your pitch. You should be getting about 10 degrees. If not either put your pushrods further out (to increase) or closer in (to decrease) on the collective servo horn. Once it's about right, fine tune with ATV (end point adjustment on your radio). Repeat for full low collective, where you should be getting -10 degrees.

Now that your mechanics are properly set up, adjust your pitch curve percentages to give you zero to -2 at full low collective, and plus 10 at full high collective and you are done. You will set up the idle ups and throttle hold later with the radio, and you shouldn't have to make any significant mechanical adjustments.

Hope this helps.