Unfortunatelly the API for launching calibration from 3rd party apps was removed from all of the new Tobii SDKs. One of the reasons is that it’s hard to ensure that the app will get focus and restore the window after finishing the calibration.
We have an API for doing in-application calibration that we provide to selected partners. To get access to this API please pm me your email address and a description of your project.
If you still want to run Tobii calibration tool, then the best option, I believe, is to start the process of the Calibration app from you code. The path to the calibration tool exe might change in the future so this feature is not really officially supported, but can be used under controlled environment.
Regarding fixations stream. It is removed from the Unity SDK, but if you describe your problem I may be able to help you with the code for the filter that you can apply on the raw gaze data to stablize it.