From the website:
3. Scoring differential among the tied teams. The team or teams with the lowest difference between points scored and points allowed in games vs. the tied teams is eliminated from consideration.
I would say there is room for interpretation. Equally, I would say I think your first point is correct but your second point is not. It still seems to be an elimination criteria, not a winning criteria. Thus I believe that multiple teams can indeed be eliminated if they are tied for the worst. If 2 of the teams are -10 and the other team is +4 then both of the -10 teams are eliminated and the +4 team wins. I do not think that a +4 team wins over a -1 team and a -10 team. I believe then that the -10 team is eliminated from consideration and then head-to-head immediately takes over.
But again, it's written in a way that someone thought they were being deterministic but in reality it's still open to some interpretation.