Weekly average when daily calculation involves lag (PREVIOUSDAY (or DATEADD('Date', -1, DAY)))

I have the following dataset:

dataset

The formula for storage flow is HeldInStorage (day X) + Supply (day X) - Demand (day X) - HeldInStorage (day X - 1).

So for a daily measure, the following DAX code works fine:

Complete = 
VAR StorePrevDay = CALCULATE(SUM(GasBBActualFlowStorage[HeldInStorage]), DATEADD ('Date'[Date], -1, DAY))
VAR StoreDay = 
    SUMX ( 
        'GasBBActualFlowStorage',
        'GasBBActualFlowStorage'[HeldInStorage] + 'GasBBActualFlowStorage'[Supply] - 'GasBBActualFlowStorage'[Demand]
    )
VAR Result = StoreDay - StorePrevDay
RETURN Result

But when I try to get a weekly average, the following formula fails (probably because of wrong filter context, I think)

AvgStorageFlow = 
VAR LastVisibleDate = MAX ( 'Date'[Date] )
VAR NumberOfDays = 7
VAR PeriodToUse =
    FILTER (
        ALL ('Date'),
        AND (
            'Date'[Date] > LastVisibleDate - NumberOfDays,
            'Date'[Date] <= LastVisibleDate
        )
    )
VAR Result =
    CALCULATE( 
        AVERAGEX( 'Date', [Complete] ),
        PeriodToUse
    )
RETURN Result

What's the DAX code for calculating weekly average of storage flow?

PS: I already generated a Week End Date column in my calendar table with the following:

Week End Date = 
CALCULATE ( 
    MAX ('Date'[Date] ),
    ALLEXCEPT ('Date','Date'[Week Number],'Date'[Year] )
)

dax