Hi Shane,
You will only be able to use Freemarker with entities that have an N:1 relationship. You cannot use Freemarker with entities that have 1:N relationships. For that reason, it is not possible to dynamically reference data from the Email Send itself.
In order to workaround this, you will somehow need to get the information into some accessible location on the record you are sending the email to or onto a record that is connected to the recipient's Lead/Contact/Account via a N:1 relationship. This blog post may be helpful: http://blog.clickdimensions.com/2015/09/making-child-record-data-accessible-to-dynamic-content.html
If you have additional questions regarding this, I would recommend that you open a Support Ticket at support.clickdimensions.com.