Hello! Is there any way you can access your Steam account some other way? Because if you can, you can actually extract the individual DLC files from the Steam version and transfer them to the Mac version, as they are cross compatible. They're found in the "game" folder of the game's main directory; I can give you detailed instructions on how to find them if you need help.
Viewing post in Our Life: Beginnings & Always - Step 3 DLC comments
Perfect. Once you're in Steam, right click on Our Life, and go to "Manage", and then "Browse local files". That will open up the game's directory. In there you'll see a folder called "game". Click in there, and look for the .rpa files (they'll be called dlc_step_1.rpa", for example). Take all of those RPA files out, and put them in the "game" folder of the Mac version. That is a bit trickier to find, as it's very deep, so here is the file path:
OurLife.app > Contents > Resources > autorun > game
Hope that helps, and thank you for playing!