control dc dc converter board with the microcontroller
The question isn't really clear… however:

yes, you can read the battery voltage with a voltage divider, but the MPQ should already have a register for that;
you don't need an high side current sense, the MPQ already has the IMON signal and you only need to read it; the board conveniently has a pin that takes that out;
you do not need to generate a PWM, the whole sense of using a programmable power converter is that it does all the dirty work. You only tell it how many volts you want;

To interface to your STM32 you only need the ground and I2C signals; check if they are 3V compatible but they should.