Microstepping is achieved by making the motor coils work against each other so it is never going to be as precise as full steps.
Whaaaa? :o
The phases are 90 degrees apart, you could not make them "work against each other" even if you tried!
Some people have a mistaken view of microstepping where they think if you set 1/8th microstepping, on a standard 1.8 degree motor, the motor will turn exactly 1.8/8 degrees with every step input.
You can't expect that.
What you can expect, and the whole point of microstepping, is that the motor will go from 0 degrees to 1.8 degrees much more smoothly than when full-stepping.
In any case, I don't think that motor with the 30 ohm (!) winding resistance is a good candidate to get 'accurate' microsteps out of.