Jamieson, Fausset and Brown on Job 6:9

9. destroy--literally, "grind" or "crush" (Is 3:15).

let loose his hand--God had put forth His hand only so far as to wound the surface of Job's flesh (Job 1:12; 2:6); he wishes that hand to be let loose, so as to wound deeply and vitally.

cut me off--metaphor from a weaver cutting off the web, when finished, from the thrum fastening it to the loom (Is 38:12).