Here are consistencies not addressed as often in the script.
Not about the OM, lies, finding one's self, or life on the other planet. This is serious.
You're the only sane one and your son depends on that from you. This is not what you expected or wanted but it is for you to deal with. Do not sit around thinking this person is going to become normal any time soon. She is currently happy seeking what she now defines as normal, and has no incentive to change.
Any change from her will only come in time, and if it does, it may not be the kind of change you would hope for now. Do not plan around her. Take care of yourself and your family. She is losing weight on what others here call the Divorce Diet. She is going through the "emotional divorce" that would come before an actual change. It may not bring her to her senses. Be very careful what you say or print about having enough money to buy a house. Make sure your screen name does not match a web search of your real name. If so, it is easy to change here, and wise to do.
You two have a child. At the moment you two aren't friends, she is not who she was. You are parents with shared financial and legal interests. You need to start considering how you'll protect yourself and your son from insanity. She may have some legal rights, and she may find some incentive to take a financial interest in any assets you think you have, whether you believe this or not.
I assume you can find a legal professional in your area that will allow you one free consultation to determine what course(s) of action you should be prepared to take, or defend. Right now you may not see your son living every other week with the OM and his kids, or sending half your financial interests across state lines. Things do not always get resolved the way we think they will.
Talk to someone about your need to document her current living arrangements, your finances, or her fitness to parent your child. Your expectations or ours do not always match the court's interpretations and do NOT assume this person will not have you in front of a judge before she comes to her senses.
Her OM may not want to change diapers either, but he or her friends may coach her into defining what she may rightfully try to claim. Your position may actually be stronger for now in your parents home if that contributes to the welfare of your son. I don't know. We here don't know. We do want the best for you all.
These concerns would not flash in front of me if I had not seen so many cases of insanity inflicting extreme unreasonable suffering upon those left in the wake of MLC (or QLC for those claiming to be too young for MLC = semantics).
Our prayers are that you care for yourself and son; that you find wisdom to do good and strength to persevere. Stay healthy. Love yourself, your son, and those that support you. Don't try turning any family against her, that's her job. She'll do quite well on her own. When her family learns what she is doing and comes down on her, expect bloodlines to turn that around into support for her and her claims.
Good Luck buddy, we really want the best for you both - but she just ain't right.