It seems unlikely the particular legal issues you mentioned are a great reason to have 2 CEOs?I would find a functional/structural reason more convincing—e.g. if there were separate orgs under EVF with ops/admin/funding needs that have require distinct attention. But this seems unlikely?
My guess is that the choice behind the duo CEO involves bandwidth and resilience if things go poorly. Other factors might be really mundane, such as idiosyncratic personal considerations that are benign and normal (e.g. Howie has duties at 80,000 hours still).
This post was well written and well structured. You are talented and put a lot of effort into this!
Related to what others have commented, I think the cost of this is much higher than what you suggest, e.g. your guess of cost using HDD storage cost and a multiplier seems crude.
Also, I'm unsure, because I haven't fully thought through your post, but some other thoughts: