Burndown with visual level filter

Hi All,

I am trying to create a burndown of remaining tasks left, based on the task end date, which falls into an Agile sprint number. Each task is also assigned to a team. Sample data below:

This is the best I have come up with:

burndown = CALCULATE(COUNT(tasks[Key]), FILTER(ALL(tasks), tasks[sprint]>=MIN(tasks[sprint])))

Here I encounter two problems:

1.  It does not take into account visual filters, so I can't easily filter by team, unless I include the specific team in the calculated measure. I would rather just have 1 measure rather than create 4. 
2. There may be sprints where there are no tasks due in that particular iteration, so the column for that sprint shows as empty. I want it to still show a sum of remaining tasks left regardless.

Here is what happens when there is no filter of team - works fine

Here is what happens when I change the visual filter to team 1. Shows as 20 tasks for team 1, and missing columns of data

And here is what I would ideally like it to look like, as an example for Team 1

Any assistance would be appreciated!