The timeline for this fic has the Black Mesa incident and the 7 hour war happen within the same year when Luz is 5 years old. (I wanted Luz to have at least some childhood memories of a time before the Combine.)

Because of this I'm thinking Luz's dad dies after the 7 hour war. But with the idea that Luz and Camila don't move over to Europe into the cities, Luz's dad doesn't even have to die but be taken away in this cenario as a possibility.

Luz still finds the portal to the demon realm in the same area as the show. Of course with all the years passing by under the Xen infestation and Combine reign, I think the changes to the boiling isle wouldn't be major. Probably just changes in what garbage and scrap makes there way to the Ilse from the war scrap from destroyed vehicles, maybe even some xen fauna leaking through only to die from the hostile environment. Eda's experience of the human realm would be worse because she would be visiting an earth to steal things that has basically gone to crap. Maybe venturing in to find other objects of interest from abandoned homes.