Hi: Put a 3/4″ bolt or steel rod into the nipple. You may need to use something smaller if the 3/4″ size doesn’t fit. Once that metal is snugly in the pipe nipple, you can put a big wrench on the nipple and apply force without crushing and tearing off the nipple. One trick is to put the wrench in place, push it pretty hard and then use a small sledge hammer to TAP on the wrench and get the nipple to budge. You become a human impact wrench 😎 It even works for old guys!