I'm sure, that every companion will have some quest, that will change their alignment, so yeah, it might be, that Astarion can become neutral, who knows. I see him as chaotic evil at the time of EA, but we haven't seen most of the big companion quests. I base that more on his general behavior and approval than on the fact, that he is a vampire. I play mostly good characters, who want to help, and Astarion is so not ok with that. That is my personal take on his alignment.
I agree, that Solas is pretty messed up and I think his racism comes from the fact, that he has a hard time dealing with the modern world and younger races.
I'm very ok with having totally different opinions and I don't want to talk you out of yours. That's often the peril of just seeing the written text, a lot of a persons intention might get lost.
I can agree with that. That's how it is with my companions as well when I do a good playthrough vs an evil playthrough.
