I dont't think your stationary engineer has ever megged a motor. 4k to ground is unheard of. I don't recall the right hand rule of thumb, but what you got sounds just fine. I prefer to have data from the mfg, but you can't always get that, so what you did is just what I would do, go get a new motor and compare the only other test you could do, that I don't see you've done here is a megger test between the "T" leads, but I don't think you'll find anything aberrant here given your other readings.
