"Clicking on a blank space" causes FileMaker to Commit the Parent and Portal records. You can eliminate the need for the mouse click by adding in an OnObjectExit script trigger that does a Commit Records step. Best bet is probably to set this on the portal so that exiting the portal or changing portal rows trips the commit records step. You can also experiment with using it with OnObjectSave on the individual fields, but since this causes the layout to "lose" the portal row focus, the results may not be what you want without some extra scripting to capture the active portal row number and then return the focus to the correct row and field after committing the record.
And even with the script trigger performed Commit, the summary fields in the portal rows will remain empty while you are editing the values in your portal row fields.
Another option is to use additional relationships that directly match to the records so that no portal filter (nor any portal at all) is need to match to the different sub sets of records. This requires creating additional table occurrences of your portal's table--each with a different set of match fields, but then you can use calculation fields defined in your layout's table that use Sum or another such aggregate function (count, average, min, max...) to compute the same value. These values will update much more smoothly than your one row portals with a summary field inside them.
Thanks commit records works a treat.