Forget about event.source.source.info and all of that. You don't need it, unless you want to apply the values to the metadata of the file.
What you do need to make sure is that the stampName value is correct. To do it apply the stamp, even if it's not working correctly yet, to some file, and then select the stamp annotation you just added and run this code from the JS-Console:
It will print out the value you need to use as the stampName in your code.
One other thing, although it's minor, is that if the code above is the custom calculation script of Text1 then replace this line:
output1.value = oDlg.strField1;
event.value = oDlg.strField1;
Instead of "#1MmYgzwIvYfvvgcFEWQfSA", you need to use the first part of the template name you've used. When you create a stamp, it is actually a page template, and every page template has a name. Usually you call it something like "Template1", or "Additonaflinformation", or whatever describes the template page. For a stamp, you have to follow a certain pattern. The template name is always "InternalStampName=Stamp Name the User Sees". For dynamic stamps, you also add a "#" at the beginning (so that your internal name becomes e.g. "#InternalStampName") - this hash mark indicates to Acrobat that the stamp scripts need to be run every time the stamp is placed.
So, when you created the page template, what name did you use? Use that in your script and it should work.
You are correct. Code is fine. I was not creating the stamp files correctly and after redoing it I was able to get the correct stamp name and get the stamp working. Thanks for the help.