Daisymae,

I have around 50 BB bushes of different types now..yes I am an addict so will give what advice I can.

Southern highbush and Rabbiteye can cross pollinate BUT they bloom at different times on mature bushes so not an issue.

Any cross pollination will be beneficial and will make for larger berries......there are no draw backs to cross pollination between varieties unless you wanted to keep the seed and nobody does that.

Yep same row would be fine.

Whether to move it is a tough call...how many hours of sun does it get? How long has it been in that spot? Is it growing well and producing?

You didn't say how you planned on planting them or in what. How you plant the bushes and what you add to the soil is the most important step and is the difference between bushes that grow fast and those that simply survive.