In addition to the advice to seek professional psychiatric help, for what it is worth, I think you should also consider talking with an attourney experienced in family and mental health law. While many forms of paranoid psychosis (which, in my totally non-professional opinion, this is) are completely treatable or at least manageable with pharmeucitical therapy, this requires cooperation on the part of the patient, which with someone who is in a dissociated psychotic state may be impossible. Even if you can get someone in such a state on an effective therapy, they may elect to discontinue the regime once relief is gained owing to the side effects of medication, resulting in relapse, and this may require forceable treatment or temporary committment. You may need good, sound, objective legal advice beyond what a psychiatrist can offer, especially in regard to marital, property, and child-rearing rights, and it would be best to get the foundation for that in place now before things get worse. There is no reasoning or using logic with someone in that situation, and while you clearly want to do what is best for her, you first need to protect yourself and especially your son.
With regard to your son, I think it best if you–or if you don’t feel comfortable or qualified to do so, a professional–explain that his mother is having some mental problems, that it’s not her fault, but that he can’t take everything she says as truthful. I say this from experience; I believe that my mother was an undiagnosesd paranoid schitzophrenic and I coped with her crazy alone for several years before it became apparent that there was nothing I could do about it or was doing to cause it.
Good luck to you.
Stranger