Custom Date Table slicer causing data to vanish

Hi, the inactive relationships between the 2 fact tables are ones which aren't needed for the report we're building so have been left inactive as there can be errors with creating a looping relationship. There's several times where account and incident are linked in Dataverse, but the Active Relationship is the only one we're currently using as it's the Primary relationship between them.

The slicer is present in the top right of the last screenshot, and it's working from the created on data of the Incident table:

The end goal is to use the filtered Date table in calculations. Many of the fields in the table are calculated columns which return a value if the Case is within a time frame (i.e. If the Completion Date of the Incident record is within the current month, return 1 otherwise return 0).

This currently works off of two calculated columns I've created to find the first and last day of the current month however the client has requested interest in being able to select the month they're interested in so I need to be able to find the first and last days of a dynamically selected timeframe. The eventual plan for this is to use the list of dates in the filtered Date table, but the first step before that requires getting the Date table established