"I know many small asteroids can break up while entering the Earth's atmosphere, but they are also traveling well in excess of 30,000+ mph when they hit it. I'm talking about a controlled drop from low Earth orbit. These blocks wouldn't be traveling faster than 17-18,000 mph."
How are you getting them to LEO?
"Plus, their angle of entry could be controlled so as to minimize the shock wave."
How would they be controlled?
" If something as fragile as a space capsule can be safely deorbited then why not a large solid block of high grade iron-nickle ore? "

The important factor is the density of the object. A space capsule has an overall low density. E.g. a capsule would easily float on water, whereas any rock sinks in water. And "large solid block of high grade iron-nickle ore" would be more dense than normal rocks. The bigger and denser the object the less the atmosphere slows the object down.
(Your block could be hitting the ground at +10,000 mph [boom])