combining dax

1. PercITSS =

( [A. SumITSS] / [A. SumReq] ) * 100        //This is the primary measure

1. SumITSS =

CALCULATE (

    [A. CountITSS],

    FILTER (

        ALL ( DateTable ),

        DateTable[Date] <= MAX ( DateTable[Date] )

            && NOT ( ISBLANK ( DateTable[Date] ) )

    )

)

1. CountITSS =

CALCULATE (

    COUNT ( sc_req_item[u_initiating_medium] ),

    FILTER ( sc_req_item, sc_req_item[u_initiating_medium] = "IT Self Service" )

)

SumReq =

CALCULATE (

    [A. CountReq],

    FILTER (

        ALL ( DateTable ),

        DateTable[Date] <= MAX ( DateTable[Date] )

            && NOT ( ISBLANK ( DateTable[Date] ) )

    )

)

1. CountReq =

COUNT ( sc_req_item[u_initiating_medium] )

Just starting out with Power BI

It’s taking five measures just to create "the percentage of requests for "IT Self Service" for one graph below.

How can I simplify this into one measure?

Also I’d like to create 3-line graphs "Previous Qtr", "Current Qtr" and a 15-month running trend.

Is there a way to have a dynamic card showing the total percentage for their respective Qtr or 15 months? The one in the graph is static “Card” so even if you change the number of months it'll always show the same.