Hi Hauntedfury,
I'm very interested in robotics. My suggestion regarding you problem is to find a different type of motor to handle the torque. You still can use the same mech design instead, just find the right size of motor to replace the stepper motor. There are lot of motor on the internet that we can use. I suggest, you use a worm gear type motor or a reduction gear head motor with mechanical break. This is because you are designing a robotic arm, the arm should hold it position if we want to. Tq
'Learn till you die'
Pian.