The fundamental problem is that damage and weight are on completely different scales. Plausibly speaking, 'transform' and 'destroy' should be the same magnitude of effect, which means if we leave the weight table alone, we should actually have a damage table sort of like this
Code:
Energy Weight Damage
-2 1 lb 1d
-1 3 lbs 1d+2
0 10 lbs. 2d
+1` 30 lbs. 3d
+2 100 lbs. 4d+2
+3 300 lbs. 7d
+4 1,000 lbs. 10d
+5 3,000 lbs. 15d
+6 5 tons 20d
+7 15 tons 30d
+8 50 tons 45d
+9 150 tons 70d
+10 500 tons 100d
Separately from that, your 100 kJ figure is seriously high. My numbers mean that a 1 lb unliving object (4 hp) needs to be moving at 25 yards per second for the correct damage. That's an energy of 118J (not kJ).