A full step sequence is made of 4 movements, hence the 0.045 degrees per movement, if you are able to discern finer than that (micro-stepping) without an instrument, you really have an exceptionally good eyesight. Congratulations!!
The current limit resistors' value is calculated the following way:
R >= (Vps - Vmotor)/Imotor
Resistor power rating calculation:
P >= 2*(Imotor * Imotor * R)
Where P = resistor power rating in watts, use next commercial value equal or higher than the calculated value.
Imotor is the maximum specified current for your motor
Vps is the power supply voltage
Vmotor is the specified motor winding voltage
R is the value of external resistor in ohms, approximate to the nearest commercial value equal or higher than the value calculated.
You could use 2 resistors (in series respectively to the center tap of the phase windings for 6 wires motors) or 4 resistors (one respectively in series with each coil winding for 8 wires motors).
My 2 cents: if you are doing this for learning , please, continue spending money on parts and further experimentation. I also advise to read more about stepper driving at: http://www.cs.uiowa.edu/~jones/step/ in order to understand what you are seeing. If you want real micro-stepping results, please, use the original lini-stepper schematics and give it a try, you already have half of the parts for it.