I have one little idea that might help-
Even though you already know how to ride, it sounds like you might benefit from going to a big empty parking lot with your new bike and just riding round and round and doing figure 8's, stopping and starting a lot. Doing this can really help you get a feel for the new bike and it can improve your handling and steering skills so you won't be so twitchy and nervous around others. Plus, the more you eliminate twitchy handling issues by more maneuvering practice, the more accurately you'll be able to tell what problems are actually due to bike fit and not due to 'new bike syndrome'.
Sundays are particularly good for say school parking lots to be empty.