Well, I finally got back over to mom's house but things didn't quite go
as planned...

I received the adapter fitting you gave me the link to:

https://www.amazon.com/Anderson-Meta...male/dp/B0070T
VKBM

I threaded it on the existing stub out, but it still stuck out about a
1/4" too far from the wall. No worries, I bought a trim ring too, so I
stuck that to the shower wall with some plumbers putty and starting
screwing on the tub spout (hand pressure only). It was all going so well
until I was about 1/8" from seating the spout. That's when the pipe
inside the wall broke loose! Dang.

So, I removed the tub spout and fitting. Couldn't get the stub to come
out through the hole in the shower surround, so I let it drop inside the
wall. I looked inside with a flashlight and could see the elbow that was
soldered to the pipe slipped off the end of the pipe. Bad solder joint.
Grr...

I did some measuring to see what was on the back side of the wall, then
used a long screwdriver to make an exploratory hole into the adjacent
room. Naturally, it was right behind the toilet (not the shower as I
originally thought).

I removed the toilet tank, and cut a small 6"x8" access hole so I could
get inside the wall.

Whoever the "professional plumber" was who installed this did a terrible
job. Not only was the solder joint bad, but they did not anchor the drop
ear elbow. They had simply hammered one of the ears into the side of a
stud.

Fixing this will be tricky since the pipe runs right alongside a stud.
There's certainly no room to get in there with a torch next to the stud
and plastic tub surround, even with a heat shield.

I'm not crazy about sharkbite fittings, but it seems like the most
workable solution in this situation. Unfortunately, I will need to cut
the pipe back to get clean pipe. I'm not sure how I'm going to get in
there to cut the pipe since it's right next to the stud.

Assuming I can get the pipe fixed, I need to figure out how to secure the
new drop ear elbow from the back side.

Sheesh, this was suppose to be such a simple repair. I'm about ready to
say screw it and let the next homeowner deal with it, but it has become
something of a challenge now. I'm determined to fix it!

Yeah, the next homeowner will probably come in and gut everything,
ripping out my proud new work, but I'll have peace of mind.

Anthony