Something you ought to consider - call up and get some time with the DB coaches. It is expensive, like $390 for 3 sessions, but these people are professionals and they are very wise. It is a good way to bootstrap your efforts, if you can afford it.
Regarding: "one of us needs to move out" .
This is tricky.
#1. if you consider moving out (and I'm not recommending it), see a lawyer and discuss it thoroughly, BEFORE you move out. Take a lesson from me.
#2. this is a trap for you! If you agree, then you are moving apart physically. If you disagree with her request, then you are arguing with her and alienating her emotionally.
Your challenge is to validate her concerns (active listening), without getting railroaded out of the house. "Yes, I hear you, you think that one of us has to move out. Wow. Let me think about that. I hear what you're saying, totally. But it seems like such a big step. I'd like to think about it. "
(Buy yourself a couple days)
By all means, you must avoid arguing with her. If you feel yourself or her getting hot under the collar, ask for a timeout. Withdraw from the conversation. "I don't feel ready to talk about this calmly." And take a breather. Things said in the heat of the moment can spoil the relationship.
Then if/when she brings it up again, you will have had time to calm yourself on the topic. You will have had time to speak to advisors. The DB coaches can be worth the money in this case.
Some other words of caution: be careful taking advice from friends + family. They will often "take your side", feel protective of YOU, and advise you to protect YOU. But they may not be thinking of how to save the marriage. They may feel like you are being insulted or mistreated and they will want to stop it, even at the cost of ruining your marriage. So please do be careful.
Also be careful even TALKING to friends/family about your situation. It can poison the well for later. You don't want everyone gossiping about yoru situation. You don't want throw your wife under the proverbial bus. Pick a friend, maybe one or two, who you can trust. Ask them to not speak of this to anyone. No gossip. Ask them to just listen to you, but it is IMPERATIVE that they do not talk to anyone else about your troubles. Seriously. Lots of people promise to keep secrets. This is really important that they do.
If you haven't found someone close to you that you can confide in (not your parents!), you should find someone, soon.
Finally, NEVER argue in front of your child.
Maybe you have specific questions. I'll stop rambling.