I'm on a Mac Air, same specs as you. Have the same issue. I own it through Steam, though.
Work around for now: Create a normal save game. It will crash out. But after you come back in, you should be able to quick save and what not without it happening.
When I create a new character, I go until the first autosave, crash, restart, "continue", save, crash, restart, "continue", and from there on it seems to be stable. I've only been doing this for a day, so I am not sure if this universally fixes it, or if it just a temp thing.
Hope that helps!