Israel is doing all it can to drag the U.S. into war with Iran. Since Israel has burned all its bridges with Arabs I can't say it doesn't make sense. It's the only play. With the U.S. pulling out of the Middle East, as you point out, Saudi Arabia's best move is to make peace with Iran. It's in both their interests to get along. There's no need for them to compete. As you smartly point out, Iran has what Saudi Arabia needs, the expertise to protect itself.

I believe everything changed when Iran pin-point took out some of SA's refining equipment. The U.S., as you wrote, didn't make it so it won't happen again.

Anyway, I think you're spot on. The U.S. policed Middle East is over.