Ac voltage measurement
You can capacitively couple and re-bias the AC voltages into the range of your ADC:







simulate this circuit &ndash; Schematic created using CircuitLab

VCC is the power supply voltage of your ADC. I've chosen the resistors assuming this is 3.3 V, and that the AC signals are 16 V peak-peak (based on your saying the A1 and A2 nodes in your circuit go to -14.5 V). If I've misinterpreted, you can adjust the resistor values to change the scaling from the AC input to the ADC input.