I have to fully agree with timmers on monitoring only the current. With a little experimenting you can define your normal operating limits and take whatever action when things go wrong.

I’m a little unclear on the idea of monitoring voltages on both sides of the motor. If I understand it correctly you will need to add one more voltage divider on the lower side of the motor. That means your resistors should be almost the same as the other divider to accommodate the full voltage when Q1 is OFF. In this case when Q1 turns ON you will only read a 1/30 portion of the voltage drop on Q1 and R1 which is even less than your voltage drop on R1 only and which will force you to use one more Op-Amp.

I see no problem with a possible less than 1V error by approximating the voltage drop on Q1+R1 but this is one of the questions for iugmoh.

Regards,

Nick