Hello: There is an “easy out” type tool that has a reverse helical shape that twists down into the pipe. Understanding that the nipple is weak, there is a trick 😎 Use the easy out as far as it will comfortably go. It may get tight but not turn the pipe. Now add a pipe wrench to the exposed pipe. It will pinch the pipe to the easy out and give something stronger to grab a hold of. If there is room, use a big crescent wrench to work on the top of the easy out at the same time.
This “easy out” tool is not hard to find and doesn’t cost too much: ;)http://www.plumbingsupply.com/extractors.html