Do you have a source on which you are basing this conclusion? From my perspective, it is pretty well established that Gandalf is Olorin, a Maia distinct from M

Do you have a source on which you are basing this conclusion? From my perspective, it is pretty well established that Gandalf is Olorin, a Maia distinct from Manwe. The non-interference of the Valar in the Third Age is also well known so it is doubtful Manwe himself would appear physically in Middle-Earth. Also, all Maiar (or rather, Ainur) are the same age or, more accurately, ageless, since they existed before the world.