Let me be very clear with this here: a man telling you that he loves you but doing all of the things your husband has done isn't a mixed message. Love and marriage are two different things here. I think a lot of people get those ideals mixed up and think that those two can equate to one another.
He clearly doesn't want to be married anymore and is being a total douchebag in his ways of showing it. He doesn't know how to handle his emotions and handle being an adult. So what the hell? Your husband needs a reality check.
But you also do too. See, you need to acknowledge that he isn't sending mixed signals. I understand where you're coming from. He's your husband and you have a child. You want the marriage to work and you hope that he's just acting out but at his core wants to be with you and love you forever. And until he realizes that, nothing you hope or feel will make that so. It's tragic..and I'm sorry your husband is such a jackass.
I think you need to be prepared for him to not come back. If he does and you all are able to work out your issues via counseling or whatever you need to make your marriage work, then great. But it requires a certain level of maturity that it doesn't seem like your husband is willing to exercise. I'm not even sure what to tell you here aside from being prepared for your man to attempt to remove himself from your marriage. But you two do need to have some convos and perhaps with a therapist doing the mediating.
Nobody deserves this. A year and he walks out??? WITH A GIRLFRIEND. Well. I've heard it all now. Seriously, cut your losses. There is someone out there who will treat you better than that.
Ok.., explain to me again why you want to be with this guy? Don’t say for your child that is the worst thing you can do. Trust me, I was that kid. Leave his @$$, you don’t need to raise two kids. Let him play the every other weekend role & find a real man.