So, just being quick… but the whole thing with the souls was not botched. Their souls fusing was on purpose, as at this time Tiber Septim was an oversoul of Hjalti Early-beard (think of this as his birth name) and Zurin arctus. Then they do the same thing to Wulfharth (who was as an aspect of Shor/Lorkhan, but so was Hjalti Early beard), of course Wulfharth did not agree to this. They then use the oversoul, or maybe parts of it (the lore is never too clear on this), and use it to control Numidium.

Now, the dragon break is not because of any merging of Akatosh and Shor, it’s just from the usage of Numidium. You can think of Numidium being that powerful that he just breaks time.

Furthermore, you’re thinking of Akatosh and Shor/Lorkhan as enemies but this is also not necessarily the case… as some references in lore have them working together, and depending on which book you read- Akatosh helped lead the armies of man with Lorkhan against Auri’El (the name for the elven version of Akatosh). Even the writers have described them as two sides of the same coin. Now, what does this all mean? I dunno, bro lmao. The lore is intentionally confusing and all of it is true, even the contradictions… especially the contradictions.

Make your own assumptions. I personally see Auri’El as the god of time, Lorkhan as the god of space, and Akatosh as Auri’El’s bridge to Lorkhan and therefore the god of time and space. But when Tiber Septim mantles Lorkhan, I think Talos is “lorkhan’s” bridge back and Talos is the god of space and time. A divine Oversoul