Hi Reuben.
I think the error that you're encountering ("Bad CPU type in executable") is mostly because the "dcm2nii_mac" executable in the DPARSFA toolbox is not compatible with the M1 Mac architecture. It's because the new M1 Macs use an ARM based processor and I believe the dcm2nii_mac executable might be built for x86 processors, more specifically x86_64 which were used in previous Macs that used Intel.
To resolve this, firstly check if there's an updated version of the DPARSFA toolbox that is compatible for the M1 Mac architecture.
If there is no such update available, then you can use a tool like "Rosetta 2" that allows you to run Intel based apps on M1 Mac.
Here's a link that can help you with the same.