I've actually learned some more since starting this. Out of curiosity I tried using VA to open cmd.exe, then copy the curl request to the clipboard, then paste the clipboard to the cmd.exe window via Ctrl+V keypress, then an Enter keypress.
When I do it this way, I get the Malformed JSON error.
There's something going on in the journey from VA to the clipboard. It looks right to me in the cmd.exe window once it pastes, but there's something off with it. I verified this by copying the request to the clipboard outside of VA, pasting and running and it works. Once I run the command via VA, the clipboard gets overwritten and the command fails again. The strange thing is that even manually pasting the clipboard back into the cmd.exe window fails until I re-copy the request from the original source.
Something's being changed...
I'll try writing a batch file next...