Sorry to ask this here, but I cannot find a comment/discussion thread?

What is the difference between "Prospector's Pickaxe Diameter" and "Prospector's Pickaxe Range" in the config?

Range is how the depth of the search
Diameter is the area that it checks in that range.

So if you're facing North and your diameter=5 and range=3, then it'll check a 3 x 5 x 5 (L x W x H) area; 3 blocks further north, and 2 blocks out each way (up down left and right)