My disablement and gaming

Hello,
I am Finn and i have an disablement on my right arm. Because of this i can only use my left hand. I am planning to buy a gaming pc but the downside is that i can't use a mouse and keyboard, i can only use one at a time. After some searching for solutions i came across the Razer Tartarus v2. This seemed like the perfect option to me. I thought i could use the keys on the keypad for schooting, walking etc. and the joystick/dpad for looking around/ aiming (like the right joystick on a ps4 controller or as a mouse). Unfortunately i haven't found a way to get the dpad/joystick to be used for looking around/aiming and i really hope if someone can help me out. It would be the perfect solution to me for playing games on a pc but the joystick/dpad is the only problem. If anyone knows anything about this or is able to help me, please hit me up!