General question: What's a good way of building Confidence up? Mine stays around 40, but I haven't really figured out how to push it past that
It's a pretty complicated stat, but basically it follows the trend of how happy Sammy has been over time. Keep her happiness high during the course of your day, and do things she likes (like exercise) and her confidence will gradually rise over time.
Also, check your perks. Depending on what she has, 40 may be her current maximum.