This isn't going to work, because a dictionary or JSON object can only have one instance of the same key. Otherwise, it'd be overwritten. So if you want to use "html", what I was suggesting would look more like this:
{"html": "Question: ...<br />Answer: ...<br />Model: ..."}
The alternative would be to use a "html_template", which you can either put in the "config" returned by a custom recipe, or in the prodigy.json in your Prodigy directory (typically in .prodigy in your user home directory) or in the local working directory.