I purchased a new stem and shower head. The current stem is about 7" and is coming out from the wall. I am having a difficult time removing the stem. Any suggestions?

That chrome stem should be screwed into a drop ear behind the wall but you could have one that is soldered. Can you remove the bonnet and shine a flashlight inside to see if this is a sweet fitting? If it is screwed in a good strap wrench should break it loose but if its soldered you could tear the drop ear loose and cause some extra damage.