. Most AC motors aren't real picky about how clean the incoming power is - variable speed drives are notoriously noisy. It should run OK with a square wave unless it it under full load, but will run warmer and may make a little more noise. If you only have ~50% load, or less, on the motor, you should be fine.

I have my doubts about using relays for the switching... for a clean 60 Hz sqr wave, anyway.

To get rid of the printing try putting it through several hot washes and tumble dryings then it should be flaky and easily removable... Not too sure bout the motor... Haven't seen anyone running any projects on non AC, because it seems simple to run it on mains...