Sven: I have read all posts in this thread. Don't be so hard on yourself. I can tell you I have been in similar positions, complied in all kinds of abuse, been taped too. It is not as easy as just saying no or just not going back. Don't underestimate the power of the guilt and the possibilities of manipulation through guilt. Especially if there is love in the picture. I have so many memories of trying to resist and then the perp would act totally hurt like I was mean all for no reason and I would end up crying and begging to be abused, feeling I deserved it, and then after the perp would say I wanted it and well, I did in a way so... This kind of manipulation is deeply damaging and still in my 30s I fall for it. So don't judge yourself.
Also, it seems you end up in a catch 22, feeling guilty when saying no and then feeling guilty after accepting abuse. There is really no way for you to not be guilty in this, right? Which is a very effective means of manipulation. Guilt can be so hard to bear, sometimes the physical pain is easier.
But having said that, please take the chance to to leave when you can. Remember the guilt you feel is not for real, you are not guilty! It is just a very difficult feeling to handle, but it is possible to deal with it and it can go away (or so I've heard...)
I also want to say that I admire you'r courage in calling that hotline, trying to help the little kids. Since I'm actually a socialworker in another european country I can tell you that at least here, you can not report anonymously if the social services get your identity. If they know who you are they have to tell the people being reported. You can avoid giving them your identity and just tell the report, then they are obliged to investigate at least a little bit. They do not get back to you about how it goes because there is secrecy and you don't have any right to now (wich is frustrating of course). Problem is it takes a lot to remove children from parents and often parents can just lie and there is no way to get any proof. So I hope something happens that saves the kids but if nothing happens remember it is not your fault, there is probably nothing you can do and you did what you could.
Please take care of yourself. And do share, maybe it will help you sort out the guilt.