sexual play

My daughter is 5 years old and her step brother is one month short of turning 8. he seems to bully her, hiotting, punching, throwing things at ehr. it has gotten worse lately, they were horsing around on a bed when we went for dinners at my ex's parents, she fell off on to her bum....we explained they needed to be careful and just sit and watch the movie. 5 mins later i went upstairs to check on them and my daughters lips were swollen and she was bleeding...she told me that he shoved her off the bed...she also said he laughed at her! I was concerned because when i asked him about it he looked at me and said "i pushed her by accident" he showed no remorse at all for her, didn't even come down when i put ice on her lips to see if she was alright. i ended my relationship of 4 years because his father refused to do anything about his sons behaviour which has been escalating. he has been in trouble at school for hitting a teacher, hit other children...he also left the school with another boy and tried to get in to a mustang! my ex blamed my daughter. my counsellor called CAS to just speak with them and see what they think about the boy, they had concerns. later that night my daughter disclosed to me that he had been on top of her with his pants down and said that "this is humping" she also said he wanted to touch her vagina and her bum....i role played with her about the doctor game she mentioned and he fixed her ears, then her boobies and then her vagina, he had a pencil in his hands the entire time with socks on his hands for gloves. he told her not to tell me, he also hit her after the game was done. she said he always told her that if she told me that he hit her that he'd hit her harder. I have had a mereting with the childrens aid society and they have interviewed my daughter. they seem to be taking it very lughtly and acting like this may be normal....i don't not think it is...any input or advice? am i crazy or just over analyzing this???!! i should also mention that this boy had to wear a weighted vest in school on year for some reason, i do not know all the details. also he can't seem to ride a bike well even with training wheels, or ice skate....he played violent video games from the age 4 and on, such as grand theft auto...he only wants to play video games, he is twice the size of my daughter as well....the father and i also have a 6 month old daughter together so my concern is for her as well. i feel so stressed out and now i can't seem to get my daughter to talk about the incidents again, like she's regressed or something! so confused. she does mention things ehre and there like, he wanted to use this, refering to my tampons, she told him that i use them in my vagina for my periods and he said to her that he had never seen me use one but she said that it was a bad idea and stuff so they just put it in her hair...not too sure what to think there!!

[aalaiyah]

i forgot to add that my daughter says he says the f word, s word, pretty much all the swear words and calls her tehm too....she said he also says things like shiny vagina, shiny boobs....bum everything basically...he says things like sexual, penis, tha sort of thing.