Count working days and toggle include today or not, taking into account holidays

In the attached example I am counting the number of working days in the current month excluding holidays, where the holiday dates are input by the user. It also lists the number of working days so far, and the number remaining (again also taking into account any holiday dates entered).

I have a couple of issues here that I need help with please if possible.....

Firstly I find myself having to put a -1 in at the end of the formula for total working days some months, but not others... but I can't figure out why this happens.

Secondly, and this is the main thing I want help with... On a given day, the formulas will calculate the number of days to go and days remaining including today. I want the user to be able to decide easily if today should be included or not without having to edit the formulas.
So I added a checkbox for 'include today', and do a plus or minus 1 on the formulas for whether it's checked or not (using a linked cell), and realise its going to be rather more complicated due to having to take into account todays date.

Whether the checkbox is checked or not should effect the number working days left to go, and the number remaining, only if today is a working day, ie. today is not a weekend day or one of the holiday dates input by the user. This surely is doable but I think a little beyond my current skill level.

I think you will get what I mean if you have a go at the example, any help is much appreciated.