That is a very interesting read and you have made a lot of interesting points.
With regard to the many names of Odin/Woden, I think the evidence could suggest both of your ideas. Some of Odin’s epithets seem to be related to tales about him, he thus earned a nickname or “ekename” accordingly, for example, Hangaguð – “The Hanged God”; some of the other epithets, notably Alföðr – “Allfather”, might suggest his gradual absorption or usurpation of the roles of other deities, Týr coming to mind, that were perhaps held more important before the Viking Age. The corpus of Old Norse/Icelandic material does indeed provide us with a treasury of materials, but it is only a snapshot of a relatively brief period in Scandinavian/North Germanic history and culture, and the end of non-Christian belief. The most important thing that I think we should always bear in mind is that we aren’t necessarily dealing with one, uniform and codified belief system, but rather a web of interlinked, overlapping, complementary and at times contradictory belief systems. I’d even go so far as to say that the question “What religion are you?” would quite well have been met with total incomprehension by a person from one of these ancient cultures.
With regard to Yggdrasill, it is usually accepted that the tree is an ash, however, other interpretations suggest a yew tree and, with the wealth of folklore and mythology surrounding yew trees, that might be an interesting avenue to explore. Sacred trees are found in the religions, beliefs and folk traditions of peoples in sundry parts of the world throughout the ages and I often wonder if this does not go back to our most ancient and primordial of origins in the forests of time, but that is just my own hypothesis.
The number three is certainly very interesting, from Judaism, Pythagoreanism, Vedic/Hindu schools of philosophy and belief, Celtic myth and so on, the number three repeats itself over and over again. The threefold death is also a recurring theme to be found in Norse mythology, Myrddin Wyllt in Welsh mythology and the life of the Irish saint Colm Cille (St. Columba). Another interesting number in both Norse and Celtic mythologies is the number nine, but let’s not digress too much now.
As far as tarot is concerned, I doubt it. Tarot started off as tarocchi, a game played in Northern Italy, emerging at the end of the High Middle Ages or beginning of the Renaissance. Divination with tarot cards only started in the late 18th century. Playing cards themselves came from China, along the Silk Road, via the Islamic world, so I doubt that any symbolism in the tarot decks derives from pre-Christian Celtic or Germanic belief systems, it’s far more likely that the symbolism is linked, if at all, to the ideas of the Gnostics and Renaissance humanism that flourished in Northern Italy at the time and drew its inspiration from Classical Greek, Roman and Gnostic Christian motifs.