Yeah. So we'll fix the logic levels with resistor voltage-divider circuits, and add a third resistor to each as a safety measure.

So.. I have something in mind like this, but need to build/test it first, and figure out the exact resistor values required.
Code:
  EMPEG -----VVVVV----+----VVVVV-----GND
   I2S        5Kohm   |     10Kohm
                      |
                      V
                      V 300ohm   EDIT: this one is unnecessary, get rid of it.
                      V
                      |
                     WT32i


EDIT: To clarify, I suspect something to do with the too-high logic voltages probably caused the failure. On your board, the 2.5V regulator appears to be dead as a result of Something Bad. And the I2S signals of the WT32i also seem to have died -- directly attributable to the high logic levels.


Edited by mlord (15/12/2017 23:00)