Unlike そちら (there) and あちら (over there), there's no way of distinguishing between そっち and あっち in text. :/ unless you can actually see the subject.

I'm confused about this one too. But そ is used to refer to something that near to the person we are talking with, and あ refers to something that is far from both of the speaker

Socchi is used to point at things that are away from speaker and near listener. In this context acchi makes sense

I'm curious on this as well. My best guess is that since そっち means it's closer to the listener and 'east' is more of a directional concept and not an actual pinpointable place. That the listener can't actually be close to "east" and therefore あっち to imply east is a far off place away from both of you is more suitable.

The listener could certainly be farther east than you so socchi could work in the sense of east is 'in your direction relative to myself', but not "east is near where you are" which might be what is more implied?

It's not wrong, but あちら isn't used a lot for directions. あっち is more like "that way" and あちら is more like "over there."