I don't think Napoleon had much room to maneuver. He was an usurper, a product of revolution, and new money amongst the Old Guard elite in Europe who would never truly accept him. So he has to control all of Europe in order to keep his empire safe. The problem with that is Britain, which is opposed to a French dominated Europe for various reasons, and are going to fund rebellions and such to undermine French control. Since Napoleon can't defeat Britain through conquest he has to resort to economic warfare in the hopes that they will submit eventually. But cutting off trade to Britain hurts his vassal states economies and doesn't do much in stopping Britain from sending weapons, only fueling resistance to his rule.
How to you keep Napoleon in power? Conquer Britain. How do you do that? That's a bit harder, you'll probably need to do some fiddling around in the ARW, maybe John Montagu the Earl of Sandwich remains First Lord of the Admiralty and his corruption continues to degrade the British navy. And maybe someone develops a technological advantage for France just for some extra insurance.