I like your step-by-step rundown of Saxton's explanation of what "hypermatter" really is.
Also worth mentioning, for purposes of this discussion thread:
FTL travel in Star Wars is achieved through the same mechanism that allows the conversion of bradyonic matter to tachyonic matter, and vice versa.
The elegance of allowing a single mechanism to explain two fantastic parts of Star Wars technology is great.
The ejecta particles don't provide "friction" so much as momentum. In this regard, they don't really have to be special per se.Zwinmar wrote:agreed, in the form of propellent it has to be some form of particle, anything that will provide friction to push to ship. Other than Tibanna gas I can't recall any other 'special' gasses in universe however.
Since most SW starship engines are commonly referred to as "ion engines", I assume that they propel ionized matter out their exhaust openings.
However, it's worth stating that "ion engines" may have as much to do with ions as "turbolasers" have to do with lasers.. that is to say, not much at all.