I think maybe something like attached might help you, I posted the attached to a similar request some weeks ago.
I just added a cumulative value for you (last join in script).
Hope this helps,
P.S. You could probably use interval match for that too, but you also need to accumulate the values then.
CalendarMaster_Previous7.qvw 167.8 K
There was similar question recently and I posted a hint for good datamodel here.
Basically you leave the transactions table as is and create "date link" between this and calendar table. Then you get inventory in charts using calendar dimensions and sum(Quantity) as expression.