Wow this is a tough situation, sorry to hear about it. I want to start off by saying I hope this ends well for you and the person who is also battling for custody rights as well (because no matter what you both deserve to be happy). And I also want to say there is no wrong person.
As for spells, spells about luck in legal matters are perfect for this situation. Good luck spells, spells to promote other's understanding and patience as well as your own are good ones to try. I hope you and all others around you are satisfied with the outcome :)