Yeah, Astarian wants to become the strongest vampire lord in Faerun and it will be difficult to turn him from that path.
I really don't think so. He said he just wants to kill his master and be free. I know he can lie but his dialogues are quite consistent in this matter.
Also, there is this moment in the game
I think his greatest dream is just to be free (obviously). Maybe later he'd like to become an important person in the city once again or something, but to be honest I didn't find any evidence in the game for him wanting to be a vampire lord. On the contrary even. I think it's natural to assume he wants to be an evil powerful vampire because he is an evil character and a vampire slave, but his plot doesn't seem to go there, at least for now. Who knows, maybe he can change his mind in Act 2 - or maybe PC can change his mind - but for now I'm pretty sure he doesn't want it.
Of course he could do it if it were the only way to break free from Cazador.