Thank you for the suggestion!  I was able to delete the "minimum length" in the schema as you described, but I'm still getting errors in my dataset batch when those fields are set to the empty string: "expected minLength: 1, actual: 0".  So unfortunately this is not working for me.

How do we set a data element to default to null for non-required fields in the Tags UI?  In the data element default value field, if I just turn it on without a value then it returns an empty string which causes the dataset batch to fail since the value has less than 1 character.  If I enter "null" ...

I am setting the s.useBeacon to true before the s.tl() call which solves this issue: https://docs.adobe.com/help/en/analytics/implementation/vars/config-vars/usebeacon.html

Unfortunately it is an internal site and cannot be accessed from the outside. Since the link that triggers the s.tl() call opens a new page, I'm testing this option and so far it looks promising: https://docs.adobe.com/help/en/analytics/implementation/vars/config-vars/usebeacon.html

I've got a direct call rule in Launch that sets analytics variables and makes an s.tl() call.  According to the debugger the rule fires, and I see the image request in the AECD but not in Charles Proxy.  The data never shows up in Adobe Analytics.  And to make matters worse the failure is happening ...

Can you fire the tag on the onchange event of the input tag that is your search text box?  Then the tag would fire once the user leaves the the text box.