[well yeah, 108 pounds would be overkill. Zoro is satisfied that he can still cut from a distance, but it doesn't appear that the creature intends to let them get any distance.

He flinches at the appearance and power of the lightsaber, having never seen anything like it before, but he gets over it quickly and leaps down at her call, catching up to her and keeping pace. At least so long as the tunnel has no branches off to one side or the other he shouldn't get lost, but this being a sewer, that sort of luck won't hold out for long]

Even after you cut it, it still melted straight through solid rock. I don't want to wait around to see what it can do to flesh.