It looks like you are setting up ‘lines’ but then using the whole draft (’[[draft]]’) in what you pass to Fantastical. I assume from the above that you are wanting to pass each line to Fantastical one at a time.
Maybe review an action like (this)[https://actions.getdrafts.com/a/1JL] for a way of doing something against various lines in a draft. There are a few ways you could do this, just find one that you can make sense of.
I’d also suggest looking at (tags)[http://getdrafts.com/actions/templates.html] page and the tag functions in the Drafts documentation for switching out the Drafts tag in the Fantastical URL.
Also when you get an error, it is useful to post the details of the error (text and/or screenshot) to help others in debugging what is going on.