Yup, he's completely out if you let him go. And yes, that's up to the player like you said. It's the only good way to get rid of him without reaching an early ending. Now if you pay attention to the choices, there are some highlighted in red, they are important choices, it's either you end a character path or you go to an early ending. The game has 2 early endings so far. However, if you made it to the end of v0.5. Player will no longer has to worry about early ending, cuz there'll be no more. But, keeping husband has it own benefits, the foursome lol.
And yes, absolutely, the trio is planned, i mentioned it before i believe, you can ignore every other character and just have fun with the 2. I hope i can push this game as quickly as possible.