Dynamic Filtering based on date selection

Thanks for sharing the files, and yes unfortunately direct file attachments are not available to all users. Last I checked it was Super Users only but that may have changed 😞

From what I can see, all that potentially needs to be fixed is the definition of which Acquisition Dates to include relative to the "min date" (whether fixed or relative). I may have confused the definition with my earlier suggestion.

Should the Acquisition Date be at least 1 year earlier than the "min date"?

If so, these calculation item definitions seem to give your expected result.

I've used EDATE as well since it adds/subtracts a specificed number of months regardless of days per month.

/*
===========================================================================
  Cust Dynamic
===========================================================================
*/
VAR MinDate = MIN ( 'DATE'[ActualDate] )
VAR CompDynamic =
    CALCULATE (
        SELECTEDMEASURE ( ),
        KEEPFILTERS (
            CUSTOMERS[AcquisitionDate] <= EDATE ( MinDate, -12 )
                && CUSTOMERS[Status] = "Active"
        )
    )
RETURN
    CompDynamic

/*
===========================================================================
  Cust Fixed
===========================================================================
*/
VAR MinDate =
    CALCULATE (
        MIN ( 'DATE'[ActualDate] ),
        ALLSELECTED ( 'DATE' )
    )
VAR CompFixed =
    CALCULATE (
        SELECTEDMEASURE ( ),
        KEEPFILTERS (
            CUSTOMERS[AcquisitionDate] <= EDATE ( MinDate, -12 )
                && CUSTOMERS[Status] = "Active"
        )
    )
RETURN
    CompFixed

If anything, the condition on CUSTOMERS[AcquisitionDate] should be the only thing to adjust.

Also, if it is good enough to check if a customer exists in SALES, I would also suggest adjusting Cust_CountSales as follows:

Cust_CounSales =
COUNTROWS (
    SUMMARIZE ( SALES, CUSTOMERS[CustomerID] )
)

Is this closer to a solution?