Dog barks at passersby when his dad is away

Hi all,

This subreddit has always been so helpful when training my cockapoo so thought I'd ask here for advice. He's a really well behaved little guy but since I had a baby he's developed some bad habits.

If his dad leaves the house he doesn't really settle or relax. He sits on the sofa looking out of the window. He barks at some (but not all) passersby on the street and barks if someone knocks on the door. If I close the blinds he still stares at the window and barks at sounds in the street. As soon as his dad returns he relaxes, often spending the rest of the evening cuddling up to me.

I use the command "down" and he gets off the sofa (and can't see the window) but soon gets back up and continues. I think when his dad leaves he feels like he's the "alpha dog" and must protect the family. If I cage him he's happy because he's not got to protect us. I think I need to train him to know I'm the boss, I'm protecting us and he can relax.

Can anyone advise what can we do to help this behaviour? Thanks