Mail not working url for third party app
Indeed, seems to be an issue with the reminder trying to read the "for surveypal"... 

So you need to "escape" the { } that you want to keep for the end result so they aren't processed by civi and wrongly identified as token.

I think we are using smarty to process the token for the reminders, you can try putting {ldelim} instead of "{" and {rdelim} instead of "}". 

Could you try if it works using scheduled reminder?

Unfortunately, civicrm has different ways of parsing the token using different tools (smarty is one way), so you might have one working for "normal" mails and that won't work on another part (reminders), and the workaround is potentially specific for each of these, so it makes the testing a bit more complicated than "just" sending an email.

X+

P.S. It's probably not as user friendly as surveypal, but you can quickly get something working with webform and webform_civicrm to make simple surveys directly integrated in your site, including being able to store the response as an activity of the contact.