It sounds like there are a couple of different issues.
While Trepka and others are figuring out and fixing bugs causing Mac version to crash that are unrelated to min system requirement, let me please extend my apologies for our minimum system requirements on GPU side not being clearer upfront.
Please contact us if your GPU is below min spec as identified by above and we will issue you a refund and will hook you up once our requirements are compatible with your Mac/PC.
Thanks for being an early adopter!