Ideally, the two of you sit down and write up a parenting plan that will be followed by both parents, in both homes. When the two parents feel completely different about what is best for the child, this is very difficult. I recently learned that there are parent mediators and co-parenting therapists that can help with this process, rather than entering the legal system. It does sound like you will likely need a neutral 3rd party to help you come to an agreement.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism