I think the idea that Malikah plans to use the Sun as a staging point for attacking Absalom Station seems good, but I mostly want to make sure I'm not contradicting intentions stated in later books. One of the things I often like to do when running APs is seed the early books with rumors, hints, or allusions to the BBEG's future plans.
For Q5, I don't think we have. But other objects seem perfectly capable of being sent to different planes without a Drift Drive. So I'm not clear on why it was needed here. I was hoping it was discussed in one of the other books and I just missed it.
I've read all the books except the sixth one. I too wanted to read them all before I started the game. I wanted to place seeds throughout each book. Unfortunately, reading up to book 5 has little to no information on General Kam or the Malikah. I am hoping I get more in book 6 but I'm not too hopeful. I feel like the AP is just meant to showcase the sun.