So there's a major problem with your view of Napoleon.

And decided to conquer nations anyway from 1803 until his defeat.

The Napoleonic Wars were overall a series of wars waged by the Allies to undo the Revolution and Napoleon. Napoleon didn't "conquer" but rather defeated those whom were actively threatening and invading France or French allies. The exceptions being the few military actions that actively backfired on him (the 1812 campaign into Russia and the Peninsular Campaign, the latter was never justified but the former was somewhat).

Further Westphalia wasn't as absolute as it seems I would suggest you look at this post by a friend of mine and this one by another friend that discusses how the Treaty is more based on confessional conflict that sovereignty. As such this means that the Treaty doesn't actually do anything for Internationalism and the concept of international institutions working to stopping a power was a result of Napoleon rather than anything Napoleon interacted as the Allies during the Napoleonic Era were a hodgepodge group of treaties.

I apologize but I feel that you are looking at Napoleon from the "Ogre" view point that is frequent in English Historiography of Napoleon.