And is there one of them that can explain the existance of an atmosphere?
No.
The theories offer 5 basic ideas
1) The Ice Wall is very tall.
2) The atmosphere lumps into the center.
3) Negative pressure gradients contain the atmosphere.
4) The atmosphere is infinite.
5) The atmosphere won't migrate since there is no lateral force in the FE atmosphere.
Each have been rebuked successfully.
1) An Ice Wall that would successfully contain the atmosphere would be a solid structure taller than the highest mountains and longer than any known mountain range. It would be visible for hundreds of miles. Its mass would be so great as to affect navigation and weather.
2) Since the atmosphere is fluid, this idea seems outlandish right away.
3) This idea is like saying you can keep water from running off a hilltop by digging a moat. Even the moat would fill and overflow in time.
4) Of course, every time we see that something is infinite we have to have outstanding proof before we would believe it. Since the atmosphere is mostly a solution and since we've measured changes in that solution, we know that the atmosphere is finite.
5) Since the atmosphere has pressure in all directions, this idea as well seems outlandish right away.
Well, that's my summary. I'm sure others can do a better job. Feel free to correct me or improve the list.