Based on the scenario you have described, unfortunately, it is not possible to use data aggregator for Heartbeat data. For Video Analytics solution to work correctly, VHL SDK should be used in combination with AdobeMobile SDK on iOS/Android or AppMeasurement and VisitorAPI library on web.
You can still continue to do step 1 and send core metrics (lifecycle/pageviews/interactions) to the data aggregator.
However, for Step 2, you need to use VHL SDK approach or use MediaCollection APIs if the SDK approach cannot be used.
Please follow following documentation for further help on SDK/Media API implementation:
New Adobe Experience Platform SDKs will support React Native as a wrapper plugin (similar to how we do for Xamarin, Phonegap, and Unity with 4x SDKs) over our iOS/Android native libraries in the near future.