Freezing and glitches during render

Problem: Resolve will not render out a timeline without either A) freezing the computer requiring a hard restart (not even a pinwheel, just completely frozen) or B) Embedding constant glitches throughout the exported video.

Project: 3 1/2 min music video, 4k timeline, 4k-6k footage mostly prores, basic color correction, no graphics, a few clips layered via blend modes

I have tried turning off and on optimized media, deleting cache, turning off frame reordering etc. Project directory stored locally, all project footage on Thunderbolt 2 Lacie Rugged Drive. It's mostly prores footage from an Inspire with a few clips that are MP4 (H.264 probably). The only thing I can think of is that all of the media is not transcoded to a single codec. Running out of ideas, any help would be appreciated.

Resolve 15.2.1.005
Late 2012 iMac
High Sierra 10.13.6
32GB Ram
NVIDIA GeForce GTX680MX 2048MB

So the idea to check the configuration guide never occurred to you?
Your VRAM is far too small for 4K.

So the idea to check the configuration guide never occurred to you?
Your VRAM is far too small for 4K.

This is not helpful, and makes incorrect assumptions. I have referred to the massive manual quite a bit as I'm trying to decide whether to take the leap to Resolve from Adobe. But regardless of what Blackmagic says (which I haven't been able to find explicitly in the manual), my Macbook with 16GB RAM and 1.5GB VRAM (25% less than the crashing machine) renders the timeline without the same glitching or crashing problems, but does not edit the timeline with the same ease that the desktop machine does. Shuffling back and forth between machines is not a sustainable workflow. This demonstrates obviously that whatever this assertion is that 2GB VRAM doesn't meet a mandatory minimum hardware requirement is incorrect. It may not be ideal for 4K, but it is not wholly insufficient.

Using a proxy workflow, the machine otherwise handles the 4K load pretty decently - far better than in Premiere. I can't imagine why I'd be able to play it back reasonably well but not be able to export. That just seems absurd to me. And if this was a hard limitation of the GPU, there ought to be a notification during install or when creating a 4K timeline.