Calculating Active Employees from Most Recent Record

You could create a calculated column in the employee table like

Is Latest Record =
VAR MaxRecordOrder =
    CALCULATE (
        MAX ( Employee_Fact[RecordOrder] ),
        ALLEXCEPT ( Employee_Fact, Employee_Fact[PS ID] )
    )
VAR CurrentRecordOrder = Employee_Fact[RecordOrder]
VAR Result = CurrentRecordOrder = MaxRecordOrder
RETURN
    Result

and then define your measure as

Active Employees =
VAR EndDatePerVisual =
    MAX ( 'DateTable'[Date] )
VAR RESULT =
    CALCULATE (
        DISTINCTCOUNT ( Employee_Fact[PS ID] ),
        REMOVEFILTERS ( 'DateTable' ),
        Employee_Fact[Start Date] <= EndDatePerVisual
            && (
                Employee_Fact[Term Date] > EndDatePerVisual
                    || ISBLANK ( Employee_Fact[Term Date] )
            )
            && Employee_Fact[Is Latest Record] = TRUE
    )
RETURN
    RESULT