Well, I'd say your model is great! If you're having problems with good poses, I'd take a small mirror, look at my face in it (before it cracks ) and use those expressions as a reference for making poses in a character. Your second question (creating a counterpart character) all depends on what's best for you. What'd I do would compare differences and similarities between the character ideas..if there are more similarities, I'd build from the already built model, and if there are more differences, I'd either build a new model or work off the pre made model at a minimal amount