When is Kadaj's summon materia displayed as blue?

As for the survivors. An in-game explanation for Rufus is given in Dirge of Cerberus where Vincent and Yuffie are helping to evac Midgar. You can tell Rufus is being carted away to a medical facility. The truly tyranical can never be stopped by something as widespread as an explosion. Like Shinra, they have to be killed firsthand by warriors like Sephiroth.

As to Tseng. He wasn't actually in the Temple as Cloud and the others were. He wasn't trapped.
He's a Turk which means he's tougher than average and the Sephiroth he was up against was just a wimpy clone, like Kadasephy. Since he didn't actually fight him, he only got a pretty nasty cut.