If you set your transmitter at 50% and your not getting zero degrees pitch than you must adjust your linkages (all of them) to either move the swash plate up or down until you achieve zero pitch.
Also, all of your servo arms and linkages should be at right angles when at zero pitch, the swash should be parallel to the main gear, etc. as per the instruction manual.
Once you have the mid-stick giving you zero pitch you can adjust the overall max/min pitch in the swash afr menu. Go to the pitch setting and increase (if negative number decrease) to increase the throw. Using a linear pitch curve, 0 25 50 75 100, move to full stick and adjust the pitch setting in the swash afr menu until you get the desired pitch - now check the low stick position to make sure you have the same amount of negative pitch. +/- 9 or 10 degrees is good (maybe +/- 8 if you are just learning to hover and do FF).