Unless you have very strong evidence of abuse or neglect of your daughter by the boyfriend, you would in my opnion, be wasting your time by pursuing a restraining order. Regarding CPS, I would only contact them if I had a clear disclosure from the child of abuse or neglect by the boyfriend. Otherwise they will classify your call as being for "information only" and you won't get very far.
I do not know whether you still have visits with your daughter. Did the restraining order prohibit you from having contact with her or just with her mom?
If you still have visits, focus on keeping the lines of communication open with your daughter. Don't "fish" but make sure she knows that she can always share anything that is on her mind with you. No matter what. Also, make sure she knows that her school teachers and counselors are always there to help her and listen to her if she ever needs to talk.
You don't say what your daughter said to you that caused you to be concerned for her well-being. You would need a heck of alot more than a "concern for her well-being" to obtain primary custody of her. Court's favor custodial continuity. Unless you can prove that the child's current environment is detrimental either physically or emotionally and that a change of custody is less detrimental than her remaining with mom, you will not get very far.
I think you did the right thing in expressing your concerns to your daughter's mother. I think you made a tactical error in alluding to court action. You never mention going to court before you have your proof and ducks in a row. Timing is a significant factor in pursuing a family law case and by playing the court card before you had anything solid, you gave away some of your edge. Because your ex-wife got to the court house first and won, if you attempt to get a restraining order without hard facts and evidence, it will look as though you are retaliating against your ex.
If your concerns are of the sexual abuse, physical abuse variety and if there is any validity to your concerns, then I think you would have no choice but to try to protect your daughter. If that is the case, then this is not a do-it-yourself type of project. Contact a reputable and experienced family law attorney to help you put the strongest possible case together.