Increasing stepper motor torque/speed with MyRio FPGA

Hello, 

Quick question I have Microcon SX-16 2 phase stepper motor connected directly to MyRio FPGA  trough connector MSPC, DIO lines 0-3 where should be 5V. Program that runs this motor has one case that decides if it runs or not. Second one for clockwise or counter clockwise.   For loop includes another case with steps for full step control.   

Is there any way to increase torque, speed or a better way? Motor rotates piece  of fabric around two cillinders and motor is connected to one of them so it can transport small object on it. But when the object is too heavy so  the tension between cillinders is too much it stops rotating. 

Thanks for any reply.

J.