Custom Acrobat Dynamic Stamps - date doesn't update, white space around graphic

Super frustrated with the process of trying to make a custom dynamic stamp work in Acrobad Pro DC, and if there's a community area for just downloading stuff contributed by people who've made this work, someone please tell me.

I am trying to make a custom dynamic stamp based on the provided stamps. I want a simple box, like the provided dynamic stamps, with the text "POSTED" and the date and time that the stamp is applied.

I've tried making my own and EITHER:

A: the timestamp field doesn't update and every stamp contains the time the stamp PDF file was saved; OR

B: the stamp includes the whole white page around the graphic, and overlay of a full page sheet on top of the document I am trying to stamp.

Neither of these serve the purpose. What I want should be very, very simple, and yet It. Does. Not. Work. And trying to make it work feels like a colossal waste of time at this point.

Attaching my latest attempt in the hopes that someone knows what they're doing and can tell me what I'm doing wrong.