[bojan]

You have to take one step at a time...
The torque on each shaft is inverse proportional to reduction ratio.
That means, higher the reduction ratio on particular stage, lower the torque at the input (the shaft which rotates faster).

The end torque (at the motor shaft) will be the same for the same overall reduction ratio, regardless of the reductions for each individual stage.. and of course, if we do not count the mechanical losses (friction).

That is the reason why people are using worm gears at output shafts, because this way the torque on the worm is much smaller (the reduction of this stage is high).
However, the mechanical losses (friction) of the worm gear stage are also very high (because of the way the surfaces of the worm helicoil and teeth are sliding against each other, they are much higher (compared to conventional spur gears or belt or chain reduction stages). Those losses (essentially friction) are depending on the load, so that is why the telescope must be properly balanced, to reduce the wearing of worm gear and required motor torque (in some extreme cases steppers may even stall because of imbalance).
Adequate lubrication of worm gear stage is also very important.