The animal bit, I'm torn about- on one hand, it could be an actual moral backbone on his part, or it might be the residual fear of Cazador. Cazador never allowed Astarion to drink from humans, only rats, and in some dialogue it's implied that he feared that Cazador's old orders still had sway over him.
As for the 'dead bodies laying about'- Astarion knows the only way he's getting through this is with your help. He's a troublemaker, but he's crafty. He realizes that he wouldn't stand a chance on his own, against entire groups of people who might very well want to stake him just for being a vampire, murder not withstanding. He's pleased as punch, drinking blood from a wine glass and reminiscing at the Goblin Party after slaughtering the druids and tieflings. He seems infinitely happier than at the tiefling party, after slaughtering a gaggle of innocents, as opposed to Shadowheart, who is getting herself as drunk as she can to try to forget about what she just took part in.
Astarion behaves himself as far as he knows will satisfy the group, but he relishes in violence, whether it be inflicted upon enemies or innocents.
I'm not saying this to be hard on him, even though from what I've gathered he was a shit before being made a vampire, 200 years as a slave to a demonic ass like Cazador probably dropped his moral compass down a well.
I'm not even saying you're wrong in your belief that Astarion might be more moral than I believe- Astarion is playing us, to some degree. Like I said he knows we are his surest way to survival, and he's trying to make sure he gets out of this whole situation on top.
The only way we'll know anything for sure is once the full game comes out and that's at least a year away.
Until then I'm just gonna psychoanalyze this posh elf bloodsucker until I go insane.
(Also I almost wanted to compare him to Fane but Fane's character arc was less 'growing from uppity and malicious into thoughtful and understanding' to 'local father tries to make up with his 30 year old daughter after leaving for cigarettes the day she was born and never coming back'.)
