Thank you for providing us with this very precious insight, Necro. I knew about Gandalf's metaphorical rings of smoke, but I had never got through the details of that moment in the Unfinished Tales, alongside the other aspects concerning the bitterness between the two Istari (with Saruman feeling most of that resentment, of course). You are surely free to make usage of these little pieces, Necro; I can't see any defect in that and our whole work will certainly benefit from these secondary sides of the lore.
As I read those words, the opinion I had been coming up with, in regards of this kind of lore, was greatly reinforced: it's always great to analyse the difference between these successive additions and the rougher lore of the Silmarillion, which, regardless of its brevity and obscurity, kind of constitutes the origin of Tolkien's vision and the main fundamental pillars which his saga is built on. Paramount themes that are regarded as customary and pervasive, given their recurrence in the vastness of the very lore. I therefore suppose we could set the limits of whatever addition, so that those prime principles are not contradicted in any way. For example, I and Fine decided to accept only the earliest version of Galadriel's history (narrated in the Silmarillion), entailing her joining the rebellion of the Noldor for her malice-free longing for power in Middle-earth, surviving the deadly journey through the Helcaraxë and meeting with Celeborn (a Sindarin prince) in Doriath.
The original portrait of the Silmarillion has always fascinated me for a few reasons, the most important of which consisting of the holistic approach of the narration, as it deals with all pivotal topics during the eras of Arda. An ancient, primordial and mythical conception that embodies the generalities of this universe. I thus feel that some late modifications of Tolkien himself or of his own son seem to alter the original essence of the mentioned properties. What do you think about it? I myself am a quite speculative/antiquity-minded person and a kind of law-guy too; henceforth, that explains quite exhaustively why I like to consider the Silmarillion a sort of mythical ensemble of tales, which sets the imperative rules that ought to be taken into account and determines the nature of the whole construction, as a constitution would do for a country