I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear about your situation.
When establishing a parenting plan, the judge's goals are to minimize parental conflict, ensure the child's emotional well-being and stability, make sure the child is cared for physically, and otherwise determine what is in the "best interests of the child." RCW 26.09.184. The judge may interview the children privately in chambers, depending on how old they are (usually, they need to be at least 5 or 6). RCW 26.09.210. Custody frequently goes to the parent who has been the primary caregiver during the marriage, because that's seen as less disruptive to the children.
In order to get the judge to make you the primary custodial parents, you'll need to introduce evidence of the way she's been abusing you. If you've had to seek help from a therapist, you can introduce the records. Ask the judge to order your wife to submit to a psychiatric evaluation before she can have custody. The fact that she's a stay-at-home mother actually counts against you - it means she's been given an opportunity to bond more with the children AND it means she's available to care for them during the day (more of an issue if the children aren't school-aged yet, because of the need for daycare). Her lack of income can be offset with child support, and she could wind up asking for spousal support at least until she can get her GED. So, the focus of the arguments should be on what's best for the kids not the financial aspects. If you can establish that she presents a danger to the children, the judge can deny her access to the kids until she can prove she's gotten treatment. And if she DOES try to cause you or the children physical injury, call the police immediately.
When a divorce is filed, either spouse can file a request for a temporary parenting plan, which would go into effect immediately, until the divorce is finalized. If you think she's going to harm the kids, you can have a local attorney file an Emergency Ex Parte Request for Temporary Parenting Plan, which means you go in front of the judge and explain how they might be harmed by staying with her. That would be filed at the same time as the Complaint for divorce, and it might be something to consider.
It's important that you are 100% satisfied with my courtesy and professionalism. Thank you.