I found it useful to have all input values for rows and fields that depend on one another. The one problem is that the values of this array keep changing because of possible save callbacks. But it helps in my case where I need multiple fields of one row to lookup a table entry. Variable $this only includes the previous values.
Can you add $varInput to the save callback?
https://github.com/menatwork/MultiColumnWizard/blob/master/system/modules/multicolumnwizard/MultiColumnWizard.php#L268