In order to limit what you see in the filter, if you're using measure names is to limit the datasource. You can duplicate the data source and then shift select all the measures you want to no longer see in the measures pane and say delete. This removes them from the list of options in your data pane.
You could also use pivot but because you have more fields than just these four it may not be a good option for you.
You can change the default aggregation of a measure by Right Clicking it in the measures pane, go to default properties, aggregation and choose the correct default aggregation. To change it once its already in a view. Right Click the measure on the view and go to where it says measure, then choose how you wish to aggregate it with the panel that opens to the right when you hover over measure.
Many thanks to Pulkit jain, I fixed it.