Wonder if theres going to be some Ellie/Vanessa content because I'm pretty sure you can leave Ellie on the hook while you go off for the weekend with Vanessa.
You will need to start afresh to unlock earlier scenes, there is no way of knowing retrospectively which scenes you've played through and which you haven't. If you aren't worried by this, your saves will work without error going forward, you don't need to replay for future content.