I didn't notice the intersecting geometry initially - in that regard I think it's a success... from a technical standpoint it would be awesome to see you solve this!
Not much to say here, add more geometry. There are tricks that exist like tesselation but they're not worth implementing when adding another lod will solve it.
Seemed to have partially solved the problem if the normal maps are disabled, however with normal maps on there is just a tonne of noise! Diffuse Only: Diff + Normal: