Serious concerns

 I've been divorced for over a month now, with a 20 month son. My ex and I separated before he was born. A few weeks before the divorce papers were signed. Our son started acting out again at visitation exchanges, crying, screaming not wanting to go with his father. The biting,slapping, and pinching that I had previously had gotten to stop, came back.  And in addition a new behavior started, he constantly tries to hump my head, a sort of masturbation, I've done some research and they say its normal to  hump objects, even read one case where the child tried to hump a dog all the time. re-direction doesn't work, and his violent reactions are getting worse, especially after visitations. (once a week and every other weekend, plus holidays and 3 weeks vacation)

My ex refuses to communicate with me, especially if it has anything to do with him, barely will talk about our son. And honestly keeping conversation to e-mail only and a few words at visitation was a god sent since he use to verbally abuse me every chance he got, which I repeatedly asked him not to do in front of our son, he doesn't need to hear that mommy is " F*** B****.

The Ex noted that he was humping but said a friend of his said it was normal and he will not redirect him or discourage the behavior, even after I told him I spoke with the doctor and they said it was normal but not with a person, and to re-direct them to an object, such as a pillow or blanket.

Thinking that something else was going on, especially with the visitation exchanges. I hired a Price investigator. In the course of 3 weeks, he's had 2 women spend the night while he has our son and another women was seen coming and going from his apartment with a key (not with our son). And a 4th women at halloween with 2 of her own kids.  I could care less what my ex does with his time or whom he spends it with. But when he has our son I do care what he does and who he has around, especiallywhen its clearly having a negative impact on our sons behavior.

Since I have little to no faith or any decent conversation coming from my ex, I called my lawyer, at first she said we had enough to go to court,now is back peddling a little bit and thinks this will blow up in face.

I'm not necessarily seeking visitation to be reduced, My primary goal here is to get what ever behavior is going on to make our son act out, to have it stop. I want him to have a healthy relationship with his father, but he's impossible to deal with and he's told me flat out, he wont do anything based on agreement, only if the judge tells him to do something. Which he even has a hard time doing that, likes to play games with me. (i.e. not providing all the travel information, when traveling out of town).

I feel my only way of addressing these issues is to go to court. I'm concerned about the long term effects this will have on our son. But I'm also concerned that it might not be enough evidence and his lawyer (scum) will taint as I'm just being litigious (made the arguement when I filled for divorce) and either nothing will happen or the judge will punish me for bringing it to court.

Has anyone had anything similiar happen, any advice on how I should proceed?