Yes that sounds fine. However you might want to look at the TPIC6B595, that has a FET driver built in and you would not need the ULN2803.
According to the datasheet, the max voltage is 50V at 500 mA.
Yes but that does not mean that you can use all 8 drivers running 500mA at the same time. Total for all combined is only about 650mA.