I'm a Bridge/ACR guy so I'm not of much help. From what I remember, though, when doing round-trip editing with Lightroom, you should be using Save, not Save As. If you use Save As, the resulting file doesn't show back in Lightroom (until you add it to the catalog yourself).
Opening an image as a Smart Object has the advantage of being non-destructive; any edits made can be changed later on.