If you like Celtic deities, I suggest calling upon Lugh in this situation to help you with the circumstances. Someone like Brigit would be good to protect the child. Two separate rituals. Two separate altars/offerings.
If you aren't comfortable with that, then choose the higher beings that you do feel comfortable with. Raphael and Metatron would be my pick of angels if you resonate with them better. As a healer, you may.
Be sure to give the higher being a bridge. That's what the altars are for. It's a way for you and them to connect without needing to have a whole new ceremony. Always be sure whichever two you call get along before you call them. Otherwise you may create more problems. I recommend having two, one for the legal side and one for guarding the child. It's more clear cut work that way.
It's best to leave this sort of work in the hands of a spirit because they are aware of more than you are.
When working with spirits, always give them credit, always give them thanks. Always pick spirits who's "job" it is to do what you're asking. In this way you are showing them work they already have all the authority to get involved in. If nothing occurs, then you should perform divination on it, because it's possible the deity/angel/saint/etc whatever you called, denied your request. Yes, they can do that. This is why I always ask for a sign during the ritual and will continue to petition until I get it. Give it heart, cry if you feel the need to. Explain your reasons. They generally try harder when you give them reason to become emotionally attached. That's why it's important to do your research and know what to say. Even then sometimes it's by trial and error.
For instance, when I called upon Brigit for the sake of a child, I made the mistake of asking for the sake of the parents first. I felt immediate disdain and felt her energy leaving. She apparently didn't like them or considered her only duty involving the baby. I had to revise my words quickly and after about 30 minutes received my sign that she would comply. She did a phenomenal job so I still stand by her work.
It's important to keep tabs on the situation and continue some form of prayer and offering (like burning a candle when you're home and awake) until results you desire are reached. How would you like to be working hard and the one that asked you doesn't even acknowledge your continued assistance? I'd be frustrated and leave! Many people think that one ceremony is enough, and for quick fixes it usually is, but in long term situations like the one you're in, there is no fast solution.
When it comes to "revenge" when you get higher beings with a lot of heart involved, the results could be drastic if it's as bad as you say. When they get upset, they don't play.