How can I make sure my untreated, unmedicated, + alcohlic ex-common law spouse doesn't get any legal say or sole custody in court march 1st-abusive to?

Ask your attny. There is no way to predict what will happen in court. I suggest you focus on being the best parent you can be and see a therapist with your children to help transition through a separation and or divorce. It can be hard to separate your feelings but staying calm, collected and respectful will show you are capable and putting your kids first.