This is essentially Sal and Jason’s big final moment.  Originally, I’m sure, I had some grand plan to get them back together, obviously, but since the beginning of Joyce and Walky!, like, Marcie became a real person over in Dumbing of Age, and it felt absolutely wrong and terrible to have Jason dump her for Sal while she was hospitalized.  (I mean, I also didn’t originally intend for them to get together while Marcie was hospitalized, but it kind of happened and you can’t really ignore that sort of thing once it’s the reality within your story, so.)  But Marcie was kind of a plot device, and then she became a person, and I figured that this bittersweet moment of Jason and Sal bonding over their could-have-been daughter was good enough.   Not everybody has to get together at the end.  You can decide they do, if you want.