It looks like tokens are not resolving right now; I've logged a case with support. Here's a screenshot from some of my testing this weekend:
http://cl.ly/image/0m0M263J3434.
1. I would create an idea for this as I don't believe it can be done using the current setup. Try setting up a link on the image with the url {{my.Save the Date}} (or whatever your Calendar File token is named) and let us know.
2. I don't think HTML will be supported, as the dialog is only a textarea field.