The Dairangers last names are their star designations.Meaning Ryo is Ryo Tenkasei, Daigo is Daigo Tengensei, ect. Hey, the Gorangers names spelled out Cassiopeia, so why not.
The real Shadam is still out there somewhere.He knew that the power of the Gorma Emperor causes insanity, so instead of taking it directly, he created a proxy to use in his stead. This also explains how the Gorma were able to revive 50 years later.
Daijinryuu is an Inevitable.Inevitables are powerful mechanical beings, Lawful Neutral in alignment. Their purpose is to enforce natural laws. Daijinryuu is extremely powerful, mechanical, and definitely Lawful Neutral, and exists to maintain the balance between opposing Ki Ryoku and You Ryoku forces.