For the first sentence, first I would remove the "the" so it's just "We are where words end". HOWEVER, while this is grammatically correct, and may be understood, it isn't a normal expression and sounds very poetic. You could maybe use it in a song or a poem, but you would probably confuse people if you used it in conversation.
A more natural way to say the same thing is "Words fail to describe this situation" or simply "words fail me/us" (note that these too are still relatively formal).
For the second sentence you should use "it" not "them"
I don't sign anything without my lawyer taking a look at it first.