If you want to know how accurate this LFS is giving for information, ask them to tell you about the bala sharks. Ask how big they get, what they need to live, etc etc... sounds to me like THEY don't know.
As for the PimaFix, wait before spending your money, let me make sure that is something safe for the balas. I do know that most common medications are not able to be used for balas because of a sensitivity to them. Balas are in the "silver fish" category when it comes to medicating, and that can make things hard.
Your image isn't showing up, and when I tried to copy/paste the image, the link says there is nothing there. Can you email the pic to me at email@example.com
please? In the subject, just put "bala pic" and I'll get back to you with a proper medication for the problem. After all of this, I'd hate to see you lose the fish.
I would also suggest looking for a new LFS, and to really do your research next time before actually spending any money at this one. It is obvious to me that they not only don't know what they're doing/talking about, but their policies for returns, refunds, replacements is also a bit "off". I would stay out of that place if possible, as they're likely to only worry about taking your money. It's unfortunate, but it happens a lot in this industry.
I'm curious about why they would suggest that specific medication for a fish they obviously don't know anything about? :(