I stumbled upon your post while searching for an alternative to putting products containing petroleum on my lips.
I was diagnosed with EC about 6 years ago and was prescribed with this lip cream containing corticosteroid. It worked, until it didn't. I don't remember exactly how but I started using Vaseline and it yielded very similar results to yours. Eventually I switched to Aquaphor because I feel a little better knowing I'm not putting 100% petroleum jelly on my lips. Now I don't think that this is THE CURE because I can't go without it for too long. And I can't simply use normal Chapstick like a normal person. But I do think it helps manage the condition to the extend that I feel like I have normal lips again. I generally put it on twice a day...before heading out to work in the morning and before I go to sleep at night...and that's all I need. It's been at least 2 years since I last had a flare up--knock on wood.
Now I would really love to find something more natural that does the same job. I heard wonderful things about coconut oil. Have you given it a try?