You need to see if you can record without her permission in your state. Doing so if her permission is required without obtaining it is a problem.
There is no way to predict 100% how a custody ruling would turn out. An attorney practicing in your courts is the best source of information.
IMO, getting out of your volatile relationship should be your first priority even if the court decides your child should remain with your wife. You are better able to protect you child if you have visitation if that is what is ordered rather than if you are in jail on a domestic violence charge. If at any time you feel your child is in danger, there are state agencies (child services, police, etc.) that can intervene. Do not permit your MIL to be your child's day care provider if one is used; these people are mandated reporters and will be alert to abuse and are required to notify authorities when it is noted.
I would expect that there is a domestic violence agency in your area. Men can be victims as well as abusers. Check with them on your options. If they tell you that they cannot assist you because of your gender, do not give up; find another source of help. Your employer may have an employee assistance referral program; make an appointment if they do.
While it may be possible to obtain a divorce without an attorney, your situation is critical given the potential for violence, and you cannot risk making a mistake. One option that may be open to you now that universities are returning to class is the legal clinic at your nearby law school.
Do not sign anything prepared on your wife's behalf without having an attorney review it.
My suggestions are practical rather than legal; there are many on this forum who are better able to give you strictly legal advice. My concern is the safety of you all while you sort through the legal issues.