DC motors - Torque/Speed Relationship
There are two errors:


the torque you calculate is the torque at stall condition (with a destructive current, if it is maintained for a sufficient long time). When the motor will start rotating, there will be a back electromotive force that will reduce the current;
omega is in rd/s and not RPM


What you should do:


calculate first the torque-speed characteristic of the MOTOR (torque as a function of speed). As explained above, you'll have to take into account the effect of the back emf on the current;
combine the MOTOR characteristic with the LOAD characteristic (Torque = 0.128 × ω): the solution will give you both the operating speed and the operating torque