facetscales | facet_grid with different scales per facet

I am creating a graph divided into facets. Some of these facets need to be on a smaller scale for better viewing. I have already applied several tricks to achieve this. However, I need to change the limits and divisions of the axes of some facets.

Calling the necessary packages, creating the database and making the plot

I feel like this should be really simple, but I have been struggling with it. I used dplyr to get the summary statistics for the following tibble:

I'm wondering whether someone can help me in applying the facetscales package to create different date ranges for each facet. I know something similar can be achieved using scales = "free_x" in the call to ggplot, but I am hoping to use this to also programmatically determine the number of days by which each facet's scale should be expanded.

I have seen a related question answered here (see Uwe's answer), but I cannot get the code to evaluate correctly with dates.

I have included a short example of my data below. From Uwe's answer to the question, the I expect a list of ggplot ggproto objects that can be included as a list in the plotting function, however, the code does not seem to evaluate the dates properly.

Any help much appreciated.

I am trying to create a population pyramid, faceted across a number of regions. The problem is these regions have very different populations sizes, creating problems for the scale on the y axis (coord flipped).

I am trying to follow the method described here: https://rpubs.com/walkerke/pyramids_ggplot2 - which makes the pyramid by using negative numbers for one sex and then uses scale_y_continuous() to get rid of the negative numbers.

First i create a simple sample dataset, for 2 age groups, across two countries: