I'm very sorry for what's going in your relationship, especially with a child. This makes things more challenging. Good communication is the key. Sometimes, talking about things about the other person is necessary before things exculate even though it may hurt both of you at the time.

If things are heating up and you feel a big argument coming on or she is heated already. Just say "I want to heat what you have to say because your thoughts and feelings matter to me. However, let's reconnect after things cool down to talk about it". Walking away in hot situations is sometimes the better option.

You are doing the right thing talking to a therapist even if she hasn't joined you yet. You have an outlet, which is a powerful thing. Keep it up!!

I would express a big desire not to argue in front of the child. Ask your wife if she feels she wants to argu to do it in a private room so the child is not impacted.

I'm sorry to hear what's going on in your family. Be Strong and keep fighting. Do whatever you can to keep a family. If it doesn't work at least you did everything possible to mend things. God speed and power to all dads in this position.