You're going through a very challenging experience. Given your own history, dealing with fears about your own children's vulnerability to abuse was always going to be difficult and anxiety-provoking at times. I just want to acknowledge that really, because your dream has highlighted a tormenting question about your domestic set-up, and that must be very tough to manage. Because of your own childhood sexual abuse there's a lot of ambiguity which makes motherhood a particularly complex experience for you. You're rightly vigilant - you've known, to your own cost since you were a child, how vulnerable and at risk children can be with or without their parents/caregivers awareness, and that's not easy knowledge to live with. Added to that, the unconscious can be a frustrating and very challenging presence in our lives, throwing up stuff that can be ambiguous and confronting. Dreams like the one you've had recently can add to feelings of helplessness, for example. Very difficult to hold, and I hope the counselling happens soon and is as helpful as you need it to be.
In the meantime, what might be useful for you? From your post it's clear that the safety of your kids is a mindful priority, and you work hard at shielding them from opportunistic abuse scenarios. You've also done some work on yourself and looked at what you went through, which must've taken a lot of courage at times and can't have been at all easy. The doubt and suspicion that this dream has highlighted puts you in a painful position - is that entirely new, regarding your current partner, or have you wondered 'consciously' about his integrity around the children before the dream? Is your relationship fairly stable or are there significant issues between you that are/are not being addressed? The dream puts you in a powerful position by letting you catch him, which could possibly suggest something about your needs in the relationship at the moment that you mightn't be aware of. How might a metaphor like 'my partner is sexually abusing my kids and I can catch him' reflect a dynamic in your relationship, possibly attempting to compensate you for a power struggle at some level? Or could it be that part of you needs to experience the 'rescuer' role (interrupting and intervening in the abuse of your children in the dream) because you weren't rescued from the abuse that happened to you as a child, but that was what you needed then and it would have empowered you. Your inner child might still be suffering from the deep disempowerment and vulnerability that the abuse you suffered entailed.
Of course, the dream might be drawing your attention to a concrete concern that your unconscious mind is aware of, but that you haven't picked up on consciously. (Which would be very understandable for various reasons - if it were true, the threat it presents would operate at various levels and would be a waking nightmare for you.) But I don't want to speculate irresponsibly here, it's not my place. I merely want to acknowledge and empathise with your dilemma. Dreams can reveal what we're only dimly aware of or haven't been able to acknowledge consciously; on the other hand, they can be purely metaphorical. Without more information and knowing your relationship with your partner "up close" it's impossible for anyone else to say definitively whether or not there's any objective truth in what you dreamed, but it's also possible that part of you 'knows' something you haven't picked up on consciously (which would be understandably confronting and terrifying, given your own experiences as a child).
You suggested the possibility that your daughter's age is triggering unconscious associations for you. For example, you may have trusted your abuser(s) before they abused you, and part of you notices that your daughter trusts your partner. That same part of you might believe something like "It's dangerous for a girl of her age to trust a familiar man that way" because of what you went through. Just because you can be rational now doesn't mean that your inner child buys it. She got that belief for a reason and it could be very hard for her to let go of it. Now she's seeing your daughter - a part of you, in a sense - approaching the age at which your own experiences of being abused began. Again, your unconscious might be trying to heal the lingering impact of your sexual abuse by putting you in the powerful role of rescuer in the dream. Equally, it might be anxiously replaying what was a catastrophic scenario for you as a child by using 'generational' associations (ie. your children) to get your attention. What further healing might it achieve by doing that, do you think?
Like you, I wonder if recent exposure to case material may also have triggered feelings you once suppressed; working through repressed feelings can be a long process with unpredictable twists and turns. Even when you've done a lot of work on your own history of trauma, stuff can still need 'feeling through' at times and dreams are a very powerful way of handling feelings that haven't been fully experienced consciously (from early experiences where you had to suppress your real feelings about events in order to survive). Your (understandably) heightened vigilance over your own children's safety is due in some part to anxiety, and the dream might be a kind of valve that lets some of that anxiety into your consciousness so that it doesn't affect your health too much. (The body dreams as much as the 'mind', in my view they work together at an unconscious level and our dreams can reflect that.)
One further difficulty you have, that might explain the anxious dream scenario, is that you are so vigilant in protecting your children from potential abuse. Your own inability to trust life because of what it did to you creates an atmosphere in your inner world that's potentially preoccupying and draining. It takes a lot to keep in place 'safeguarding' measures, requiring part of you to be on 'high alert' constantly, keeping all bases covered, including your relationship with your partner. To a certain extent you're in a bind, perhaps unable to more fully relax and trust and enjoy your adult relationship/partnership at a significant level because of the devastating impact the sexual abuse inflicted upon you had, and still has.
I realise there are no firm answers here, but I hope something I've suggested might help you move forward from the disturbing feeling your dream left you with.