Several thumbs up to Bob for:
(a) actually calculating the gain
(b) comparing it to datasheet figures
I will note that in post 11 I pointed out the issue with the voltage divider, and in hindsight this was a big miss on my part in not following that through and paying close attention to the
datasheet.
Rich, I note that you have changed the voltage divider ratio and the gain, but I wonder if you shouldn't present an even larger signal to the op-amp. Attenuation followed by amplification is generally not a good thing. I suspect you want a small amount of gain so you can filter out high frequency noise, but I can't put any figures on that.
Also, I have to thank you for posting the images of the board and PCB layout. I pretty much ignored them once I saw it wasn't something on a breadboard with flying leads everywhere. I discounted that as a problem.
I think we've all learned something in this thread.