Aggregate Patient Claims when Exceeding Threshold

Hi PBI Gurus!  Need some help.  Here's my dilemma:

Part 1 - Table

Here is my data table example

Special ID          reporting_date           $ Medical Spend

ABC123              1/1/2021                    $25,000 

CDF123              2/1/2021                    $15,000

ABC123              2/1/2021                    $15,000   

XYZ123              2/1/2021                    $10,000         

ABC123             3/1/2021                     $5,000

The Reporting Dates are an append from multiple tables and in a separate table called 'Reporting'[reporting_date])

I created a measure called Medical Spend from the medical table $ Medical Spend = CALCULATE(SUM('Medical'[medical_cost])

Part 2 - Table with Limits

I have a table with values that are in $5K increments call 'ISL' [isl_limit].  I created a slicer visual that allows me to select a value (i.e., $5,000, $25,000, etc.).

Part 3 - Total Medical Spend

I created a table with the Reporting Date and the medical spend by month:

 Quarter     Month      $ Medical Spend

  Q1            January     $25,000

  Q1            February   $40,000

  Q1            March       $5,000

Help #1 - Cumulative Total Medical Spend

I created a formula that I would hope create the following results, but it does not work:

 Quarter     Month      $ Cumulative Medical Spend

  Q1            January     $25,000

  Q1            February   $65,000

  Q1            March       $70,000

Help #2 - Cumulative Total Medical Spend that Exceeds the ISL

First I created a measure called $ SL = CALCULATE(SUM('ISL' [isl_limit]) and created a drop down filter

Second, I created a second measure that I would hope show the cumulative amounts of members who exceed the $SL value, thus producing a table like this (where the SL value is for total medical costs for all members > $25K in spend):

 Quarter     Month      $ Cumulative Medical Spend     $ SL Medical Spend

  Q1            January     $25,000                                      $25,000

  Q1            February   $65,000                                      $40,000

  Q1            March       $70,000                                      $40,000

Special ID ABC123 Spent $25K in January, another $15K in February and nothing in March (total $40K)