I think there are a couple of ways to go about this. The most simple would likely be to stage it out the way that you have it, but also add a line item for the forecast. Both of these are based on the "Actual" line item.
From there, you can just create a new module that has the list that contains "Weekday, Weekend, and Holiday" as a dimension, and have a line item for Actual Day Count, and another for Forecast Day Count.
For the formula, you want to pull the Forecast or the Actual line item from the first line item and sum it across the weekday line item.
My formula here is: Monthly Module By Day.Forecast[SUM: Monthly Module By Day.Weekday]