But, variables are not standard in CSS. I always perceived less variables as JavaScript variables.

Now, I need to figure out a way to make Vim treat hyphenated words as words for filetype=less.

You can either use the 'W' movement (instead of 'w') or use the 'iskeyword' option to change what is considered a word character. Word movement: http://vimdoc.sourceforge.net/htmldoc/usr_03.html#03.1