Early on it was reported that Gray had 2 lawsuits going on, one for the car accident that did serious harm to his spine and a joint lawsuit with his mother for lead paint as a child. I think he was trying to self injure himself to make a 3rd lawsuit and screwed up and seriously injured himself — killing himself by screwing it up.
I agree with you. I think he wanted to take advantage of the current anti-cop sentiment, injure himself, blame the cops, and get off on the arrest charges plus getting a cash settlement in exchange for going away.
Then he slightly misjudged what the result of flinging himself against the wall of the van would be.