They launched their "most intense" wave of attacks today, that verbiage being used by the IRGC, and yet no injuries were reported in either Israel or Saudi Arabia, at least not as far as I've seen. Both nations have missile interception capability, the vaunted "Iron Dome" and whatever the Saudis have.
The reality is that missiles are probably about all Iran has left. The US and Israel have established air superiority over Iran. That much is evident from the way both are bombing the shit out of the Iranians pretty much at will. This indicates Iran's air force is largely neutralized. In the same vein Iran's navy is taking a beating. With the absence of boots on the ground, the IRGC and Basij are largely irrelevant.
I think you're also underestimating just how much the other Gulf states hate Iran. There's the Shia/Sunni divide at play for one thing, and that animosity runs deep. Another factor is Iran's ambition to be a regional power, something the Saudis, among others, definitely do not want to see coming to fruition. Iran hasn't endeared itself to its neighbors.
There's a lot going on here, militarily and geopolitically. Iran can state publicly that it won't end the war until Israel is no longer able to wage war. Stating it publicly and having the power to bring it about are two very different things. I strongly doubt Iran could outlast Israel alone, much less Israel and the US working together.
Obligatory note: This is not to say the war is a good thing or that we were justified in attacking Iran. My post is strictly my reading of the military and geopolitical situation and that's all. As I've said in other posts, I think it was folly for Trump to launch us into this idiotic war but Trump gonna Trump. Getting mad about him doing something stupid is like getting mad at fire for being hot.