I always plant trees about 2 inches high (i.e., 2 inches high measuring from the root flare not where the top of the soil is in the container). So the hole, IMHO, should be 11" deep and 30" wide. However, if the root flare is, for example, 1 inch lower on average in the pots, I would make the hole 10 inches deep in this example.

ABM's grow, on average 40 feet wide. So, maybe 25 feet apart? This would leave a little room for wider growing trees and they might not get too close when mature.

I always say 1/2 the spread is the distance from driveways. That would mean 20 feet, however, maybe some other members can answer this one better. I'm not sure if you need them to be that far from cement slabs? I say this because I see many ABM's planted in steet areas, with much less space, and they don't seem to damage the cement.

I would DEFINETLY apply wood chip mulch OVER a light sprinkling of compost or composted manure mixed with a little bonemeal around all the planted little trees.

I sprinkle a little bonemeal in the soil I put back in the hole to aid root growth. Many people say that isn't necessary anymore but I've had very good results by doing that.

Oh, I forgot to mention that I would plant the ABM's 20 feet from driveways (i.e., 1/2 the spread of the tree) because the dripline would be at the edge of the driveway when mature.

To me, that is most the visually appealing. Just my opinion though.

Thank you, you've confirmed the spacings I had in mind. And I'm so glad I asked about the hole depth and width as, for whatever reasons, I figured the holes needed to be deep and tight around the root ball to "hold" the tree firmly in place.

You're welcome. Good luck!!