Should I just null the vars I initialized in onCreate()?
Should I call something like this.runtime.removeDestroyCallback() as well?
You should remove any callbacks you added and null out any references to objects. The runtime recycles destroyed objects so you want to make sure your object is in a clean state again for having onCreate() called on the same object again later.
Develop games in your browser. Powerful, performant & highly capable.
I understand, thanks.