Well, similarly this is the first time in two decades that I hear someone lacks a right mouse click but that's alright - we'll get this working. I've asked around a bit and it seems like in the settings of MacOS you can set the trackpad to have a right click in the bottom corner, have you tried setting this up?
On the pages for purchasing Asset Forge it's listed that because the software is completely DRM-free we don't give refunds unless there's a technical issue with Asset Forge. So we'll first need to investigate if this is indeed due to a technical issue. If you like to start a refund procedure please e-mail to support@kenney.nl.
Edit: A few people tried and on their Macbook the rotating worked, they were using two fingers on the trackpad - have you tried that?