Hi Roscoe,
As to the shoulder, I 'tweaked' mine a long time ago while batting opposite handed. I thought it was just a tweak but it wound up being an injury that did take time to heal up.
As to the stance, I would suggest listening to Ms. Crimi. Yes there are many many variations on stance as we are all individuals & a one size fits all cookie cutter approach does not make sense. BUT... there are some basics that are true.
To say that the stance does not make much difference makes no sense to me as it is the foundation from which our stroke is based. It is almost like saying stand how ever you want when trying to hit a golf ball 250 yards but make it land in a 40 yard wide fairway. Try that & see how successful you'd be in hitting that 40 yard wide fairway with any consistency.
You should want balance & alignment so that YOUR body allows YOU to stroke straight with no off line influences from the alignment of the stance.
I think Earl thinks that the bridge is the most important aspect. That's why he has worked with adding weights to the left arm. Some place it very lightly on the table while others 'grab' & dig into the cloth.
Perhaps Fran can give us some insight to Earl's thoughts if she is familiar with them.
In any case, I'd listen to what she says as she has pro player insights, since she was a Professional Player before she became a Master Instructor.
Best of Luck with the shoulder & finding YOUR solution.
Best Wishes for You & Yours,
Rick