If it's all in one reservation, and you are in Business, because it is the highest class on the second leg, then you will be granted access. We spent 9 hours in the F Lounge on Christmas day, and it actually wasn't as horrid as I thought. There are rooms to sleep in in the EY F Lounge as well.
FYI - Allow 1.5 hours to get from AUH - DXB via road. I certainly wouldn't do it in 8 hours.