I think I am wasting my time with this project that is full of errors.
You did not follow my note in my attachment in post #52 about the low value of C13 cutting most high, medium and low audio frequencies but it passes ultrasonic bat frequencies well.
You have selected two mics that might be electret but the "datasheet" does not say. They are "omni", not noise-cancelling. They pick up sounds and noises all around. A noise cancelling mic is larger and has a rear port. Far away sounds are cancelled but very close sounds are louder at the front than at the rear port so there is less cancellation. A noise cancelling mic is useless for a hearing aid.
The datasheets for the mics are completely useless. Where is the frequency response curve? Where is the directivity curve?