I agree with a lot of what has been said here in terms of the majority of the issues--while I personally find them nasty--are in fact acceptable and practiced by a large number of people and certainly CPS wouldn't intervene.
|-he is often hit, slapped, screamed at, pulled around by his hair
This is horrible. And like a lot people here, my first thought was, yes, now THIS is CPS worthy.
But then I recalled a while back there was a discussion of Lisa Welchel's parenting book. Apparently one piece of advice she offers is, if your child doesn't want to hold your hand while crossing the street, that you say "I can either take you by the hand, or I can take you by the hair." The idea being that the child will choose the hand. However, I imagine if the child still refuses, her advice would be to follow through on the threat.
Now, this is in NO WAY supporting such a method. I haven't read the book and never plan to--the excerpts I've seen turned my stomach. However, I do wonder if there is section of the otherwise normal population that uses such tactics as a disciplinary tool. Of course, that doesn't make it right, but it also means that CPS likely won't see it as abusive, just as spanking isn't seen as abusive, just a discipline technique. Obviously one I disagree with vehemently, but not illegal in this country.
At any rate, they certainly do not parent the way I do, and I do wish there were someway to reach out to them, support them, and offer alternatives. Likely that is not possible. Neverthless, CPS might not be the right call either.
I think of all the things listed, likely the carseat issue is the only black and white one