There’s a 64-bit version you can download and see how that works for you. Info:

If you're on macOS and want to test if the 64-bit version of PiB works on your system, then please try out the beta version. Here's Valve telling you how to do that:

"Right-click on the game in the Steam client and select Properties. From the Properties window, click the Betas tab."

Then select "testmac64bit" from there.

it’s a miracle! you should push it to the main branch. it works!