PowerBI Last N Months Trend Line - Ignore All Date Filters

Question

Have a simple, 2 table model: [Sales]*-[Calendar] with sales that span from 1/1/2021 to yesterday. Day grain. Calendar is a standard date dimension.

Need: I want a line chart that shows the sales trend for each day since the first of the month, 3 months back, to yesterday.

I want this line chart measure to ignore the influence from all Calendar[Date] slicers/filter that happen to be on the report.

I understand I can use the "edit interactions" feature and stop the Date slicers from affecting the trend line - and that works - with this code.

However, I want to learn how to ignore these external filter affects within DAX & not rely on using the edit-interaction feature.

I've gotten this far. This code calcs the measure I want, but a date slicer on the report affects it and I don't want it to. What am I missing?

 Total $ Last 3 Months Trend = 
VAR __monthsBack = 3
VAR __endDate =
    CALCULATE ( MAX ( Sales[SalesDate] ), ALL ( 'Calendar' ) )
VAR __endDateMinus_NMonths =
    EDATE ( __endDate, - __monthsBack )
VAR __firstDate =
    DATE ( YEAR ( __endDateMinus_NMonths ), MONTH ( __endDateMinus_NMonths ), 01 )
RETURN
    IF (
        MAX ( 'Calendar'[Date] ) <= __endDate
            && MAX ( 'Calendar'[Date] ) >= __firstDate,
        CALCULATE (
            [Total $],
            FILTER (
                'Calendar',
                'Calendar'[Date] >= __firstDate
                    && 'Calendar'[Date] <= __endDate
            ),
            REMOVEFILTERS ( 'Calendar'[Date] )
        ),
        BLANK ()
    )