10 lbs of Blueberries per gallon is really high. That would be 50 lbs of blueberries for 5 gallons and hardly enough room for anything else. I suggest 4 lb/gal which would be 20 lbs and 20 lbs of honey. That should get you in the ballpark for your OG. Also, for a FG of 1.030-1.040 you might need to back-sweeten.
I've been giving this more thought and I'm considering utilizing fresh pressed blueberry juice in place of water and then adding more fresh whole berries in primary. Proposed Recipe is below.
Ingredients:
2.0 Gallons of Fresh Pressed Blueberry Juice
20lbs Orange Blossom Honey (roughly 1.6 gallons liquid volume)
20lbs Fresh Whole Blueberries (assuming that this will add about 2 gallons of batch volume)
This puts me near 6 gallons total volume. My only concern is how much extra honey would I need to compensate for the 20lbs of fruit that will more than certainly dilute my mixture.