First a note that SwipeView and its base type Container have gained some new members in Qt Quick Controls 2.1 in the upcoming Qt 5.8. These will help with your tasks:
SwipeView::interactive
Container::incrementCurrentIndex()
Container::decrementCurrentIndex()
For the time being, you could add the following binding as a temporary workaround until you will be able to use the new public interactive property:
Binding {
property: "interactive"
target: swipeView.contentItem
value: swipeView.currentIndex !== indexOfWebEngineView
}