Yes, I do think sociopaths are capable of killing. But, most sociopaths do not kill. They just become sleazy businessmen or thiefs. Also, I don't think CA made this connection until close to the end and even then I don't think she felt casey was actually capable of intentionally harming her baby.
No, casey clearly was not a good parent. A good parent lives for her child. A good parent works hard to support their child and enjoys spending time with her kid instead of dumping them with grandparents whenever they can. However, I have not heard any statements supported by another source that Caylee was ever at drug and sex parties. It seems AL and company did not want Caylee their at all.
Caylee did sleep in the bed with Ricardo and I would never do that. It's wrong unless it's the daddy. But, I've heard of no other reports of Caylee sleeping in the bed with other men.
Aside from that, and even if casey was doing all that and more, there is nothing to suggest that the Anthonys were aware at all that Caylee was sleeping with casey or being taken to adult parties. Remember, casey was lying to her family about where Caylee was (she's at the sitters).
Fdditionally, many parents make mistakes. Some do take their kids to parties where they should not be, etc., but, there is nothing to suggest that casey ever raised her voice to Caylee, hit her, left her unattended, failed to feed her, or any of the things that would have caused CPS to step in. By all accounts from pretty much EVERYONE who knew casey, she always was kind to the child, attentive and Caylee was always well-dressed, well-fed and clean. Things are never so black and white. Seemingly adequate parents do kill their children and monsters can often hide who they truly are.
Finally, it does appear that CA was at least entertaining the possibility of taking custody of Caylee, but if she went to see a lawyer, I can tell you what they likely said. I am a family law attorney and I do guardianships. The thefts, the lies, the lack of work, etc., nor, even if true, dragging the kid to parties or having her sleep in the same bed with various guys, would guarantee that the Anthony's would win in Court. If they did not, casey's anger would likely have taken Caylee from them forever. As it was, that's what ended up happening, probably right after CA threatened to go for custody.