1) Unfortunately, because the ATmega328 isnt a TI part, I'm not familiar with the device. Just connect the SDA pin of the ATmega328 to the SDA of the DRV10983 and same for SCL.
I would post on support for ATmega328 on how to communicate with I2C and write simple code.
2) We have a programming guide for MSP430 Luanchpad to communicate with DRV10983 through I2C, so I would look at that ( 
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