I successfully etched a new board (after thickening traces, etc as much as possible). I cleaned and etched the board, re-flowed all the SMD parts, drilled holes for jumpers and header pins (and hand soldered all of that stuff) it was time to check everything under the microscope (everything looked good, including continuity across ground and power nets).
Now to plug the board into the Adafruit Feather board... again nothing seemed to work! The board connected to my PC without a problem, loading and running simple programs like Blink also worked fine. Time to look deeper! Fairly quickly I found that I was getting no voltage out at the 3.3v pin even though continuity from the board to the pin seems good.
Just in case I re-built the circuit on a solder-less breadboard and hooked it up to an Arduino Uno (actually I tested the pulse sensor functions first, then the GSR and finally both together) thankfully my circuits and data capture software all still functions correctly.
In the morning I'll retest the Feather Wing board by hooking it up to the Arduino Uno to see if it actually works, if not I'll need to see what's wrong and then figure out why my Adafruit Feather board is not supplying voltage through the 3.3v pin.