Bonesaw from buckeye is good. It is non-butyl and contains a mixing indicator. Pour it in until the water is milky, then you have the right dilution for the water you are using.
Polyurethane can be a bear to strip. It can stripped with a GOOD stripper. But plan to work at it. Will require ample dwell time. Lots of aggressive scrubbing. And perhaps multiple attempts to get it all off the floor.
Or do like Michael said above. "Run and don't look back."