curbs - 1 swang - 1 cowps - 2 skimp - 1 ottos - 1 heles - 1 roped - 0Yay, a zero. And with common letters, too. This promises to be quick. Let's start by reducing from the zero:
cubs - 1 swang - 1 cws - 2 skim - 1 hls - 1Since (ts=1), that's only two options, so let's start by assuming the s. Reducing with that gives us:
We know it must be either the c or the w (cw=1). However, the c is out (cub=0), and so is the w (wang=0). We have a contradiction, so the s is out.
That means there is a t (ts=1). With the s out, we also know cw (cws=2). Reducing gives us:
Since there's probably a vowel, let's go with the i. That gives us 2 combinations, tcwih and tcwil. Anagramming turns up the solution: witch.