Hi, I am too much of a beginner to advise on motor tuning, but here is a little to get you started.
I looked in the "stepper motor" section of the forum and ran a search for "damper". This thread will get you started on that path.
Perhaps before you spend to much time targeting 150 ipm, it would be helpful to try to run your router "hand driven" to see what speeds make sense for the router + bit + material combination. I was very surprised that in this mode, my Bosch router with 1/2 straight 2 flute bits was very happy at 300 - 400 ipm - kind of an interesting experience.