This all looks excellent! If I had one small critique, it's that the subductive margin on the southern Tillerson Plate looks quite irregular, in a way that's difficult to find on Earth. With irregular plate boundaries like that I'd expect to see more offshore volcanic arcs and back-arc basins, as is the case with the western edge of the Pacific Plate or the Mediterranean Sea between the Eurasian and African Plates.

The subductive margin wrapping tightly around 3/4 of the Comey Plate also makes me a bit uncomfortable, and my sense is that the slab pull from all that subduction would make the continent rift apart in the middle. But I'm far from an expert and it looks like you've put quite a bit of work into GPlates so I'd believe you if you said it's plausible with the tectonic history and all