Debbie, as you wrote, (" Because I've never recovered fully from back surgery, most folks think I have spinal cord damage. I don't know what to say to people. Have you found, that in addition of losing so much physical functioning, that you've also lost friends too? We just can't keep up socially and were losing touch with many friends.")
First, I have read all of your posts. I think, my opinion, you are getting way ahead of yourself concerning PLS. As your Neuro told you... it may take years to get a diagnosis. Don't convince yourself you have PLS... yet.
Being you - yourself said you have never fully recovered from back surgery there are so many other possibilities. Along my 5 year journey to diagnosis, MND wasn't really brought into the picture until 8 or 9 months before my diagnosis.
You have written about having a personal trainer and doing leg presses then thinking you need a power scooter just to get around. I think, my opinion, you need to give the internet and maybe this Forum a break until you have been seen by your Neurologist several more times. As you wrote, she (your Neuro), at this time, doesn't think any further testing needs to be done. She's an expert... the Internet is not. If you doubt her... get a second opinion.
As far as friends... it separates true friends from good time friends.
Again, don 't convince yourself you have PLS... yet.