1. I'm not actually sure what's going on here - those keyboard shortcuts are handled by the code editor component (Ace) and I'm not seeing any reported issues about them not working on Mac. Someone else is also getting this so it's not just you at least. Maybe I'll be able to ask about this after I get an easier-to-test web version of editor going.
2. That'll be in the next update. Won't be smart completion like what Parakeet did (that's a lot of work) but will be on par with GMS2.