Same material as in its the same material as the other bars. You said the one Anakin broke was the strongest since it was in the middle. But it was identical to the others.
You can ask Satele to go with you on one of the Flashpoints in TOR and she says she's "not the warrior I used to be". Fatal Alliance takes place in the same year as TOR.
That's not how shapes work. One point always going to be stronger than the others. Granted it was fairly circular, but it was no arch. One point had to be stronger than the others.