There is no coherent theory explaining why the atmolayer/atmoplane doesn't just leak over the sides.
There are a few halfhearted attempts here:
https://wiki.tfes.org/AtmolayerOne idea is a massive ice wall but we would surely have observed that - and if we can't then the whole idea of empirically observing something goes out the window.
There's some mumbo-jumbo about dark energy which, had RE proposed that, would be dismissed as "magic"
And then there's the Lip Hypothesis which has it's own page:
https://wiki.tfes.org/Atmolayer_Lip_HypothesisBut I don't believe there is any empirical evidence that declining temperatures and pressures could contain a higher pressure. The flow is always from higher pressure to lower pressure.
The only hope I see is an infinite plane or a physical dome - I know both these theories are involved in some FE models but the first seems preposterous and can't be observed so no evidence could be provided for it, the second - what material could the dome be made of that it wouldn't break and what evidence is there for it even existing?