The astrology in Tarot isn't what you might call objective astrology, in the sense of maps and birth dates and things astrologers deal with. The GD used astrology in order to convey semantic ideas, which actually makes it easier to use the decans in the cards, to a a degree, without knowing astrology but only the basic attributes of the signs and planets.
Luxury, the Four of Cups, speaks much about stability of feeling, being in expansive Chesed attributed to Jupiter, and the card itself being attributed to Luna in Cancer (one could think of it as the Priestess sitting in the Chariot). However, as we are in Briah, the stability implied here is rather stale, taking feeling for granted, lack of fresh air, etc. Geburah, as the Sephira of disruption, fulfills its duty, and how it does so is explained through the decan. Mars in Scorpio denotes a certain harshness, both having warlike connotations in a fiery Sephira of Mars (although Scorpio, a water sign, creates an interesting juxtaposition here), but in the watery suit of Briah. After the stability, albeit relative ennui, of Chesed comes the inevitable end to the honeymoon and Disappointment.
I recommend you look at LRichard's cheat sheet in the Golden Dawn forum, it illustrates very well how the signs and planets are ordered, since they do in fact have an order and are not attributed haphazardly throughout the cards.
And... I feel strange saying this, you need to do a little homework. You seem to be reading a novel from the end and expecting to understand the entire plot and so to a great extent your questions cannot be answered since you don't speak the same esoteric language. What you said about Keter=Pluto, etc. has to do with the attributions of the Tree, which do not change, but interact with the attributions of the decans. Wang didn't say anything that contradicts what we're saying here. How the decans are ordered (or that they are ordered at all) is also pretty basic, assuming one has interest in such things. Implying the minors have nothing to do with the Tree of Life simply shows a lack of knowledge. In addition, expecting attributions to live up to divinatory meanings which are themselves simplistic, abridged and secondary will only get you into trouble. The purpose of all those attributions is that they be understood and then you can build the significance of the card using the tools at your disposal.
I recommend taking a step back, picking up Lon Milo DuQuette's book that explains the basic tools of the Thoth, maybe his book Chicken Qabalah, and taking it from there.
