Even that it would please God to destroy me; that he would let loose his hand, and cut me off!
Destroy - literally, grind or crush (Isaiah 3:15).
Let loose his hand. God had put forth His hand only so far as to wound the surface of Job's flesh - "Only upon himself put not forth thine hand" (Job 1:12); "He is in thine hand, but save his life" (Job 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. "I have cut off like a weaver my life; He will cut me off with pining sickness" (margin, 'from the thrum,' Isaiah 38:12).