Will this MOSFET work for Q1?
The notes for Figure 4 in the VNH5019A-E datasheet (http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00234623.pdf) list the requirements for the MOSFET used for reverse-battery protection. Figure 5 shows the circuit without the MOSFET.
What are C2A & C2B?
I don't see those in the Pololu schematic.