I had a difficult to remove nut experience a few years ago. You are welcome to read about it here, may give you some alternative ideas… Quick summary of what worked best in my situation, place vise grips snug on the nut, jaws oriented 90 degrees to the nut, twist the vise grip jaws with a wrench. An open end wrench where the jaws were oriented 90 degrees to the shaft would have worked too, but I didn’t have one. Best of luck.
BTW, IMO you can never have too many tools. The only problem with owing a lot of tools, it seems like by the time most any semi-complicated job is complete almost all the tools you have are on the floor … lol …