Seemingly, the rules were set in place that Ben and Widmore couldn't harm one another. Is it possible that Ben shot Widmore in an effort to actually save him? If Ben believed that Locke was about to kill Widmore, Ben shoots him knowing that he can't actually kill him but preventing Locke from hurting Widmore, and thus actually sparing him. (Possibly allowing Widmore to play a part in the end-game.)
I see where the thought is going, but I think you are taking the wrong path to it. Look at when Michael tried killing himself. He tried the car, but ended up being saved with virtually no permanent damage done. Then he tries the gun, and it doesn't fire. I think that the rule that says Ben can't kill Widmore, doesn't mean he can shoot him multiple times, and he is okay, but rather the gun wouldn't have worked. Whatever rule there was in place somehow dissolved.
Holland, you have a way of coming up with some really cool ideas. Always impressive. If I was to play devil's advocate, I would say that the rules between Ben and Widmore were different than Jacob's rules. Jacob's rules couldn't be broken, but we saw Widmore break his and Ben's rules by killing Alex.
But it would be cool to see Widmore show up at a time where all hope seemed lost...I kind of think thats going to be Miles' job in the finale though.
I don't know if I'm going to be the unpopular guy for saying this, but Widmore didn't kill Alex. Now don't misunderstand me, I'm not saying that Keamy wasn't there on the island because of Widmore, but honestly, Widmore didn't kill her.
