I think he gets $500M guaranteed.
One of these 12 WAR seasons to a team is worth like.... $100M to $120M on its own. So he only needs to give the signing team a handful of elite years to earn the deal.
And like you said, even though he seems like a high risk player because of what he does his double skill set is actually a hedge against some catastrophic, career ruining injuries.
So on an annual basis yes, you are always worried about injuries because of how much he does, but over the course of a decade maybe the injury concerns aren't as severe? If that makes any sense.