Is there anyway to determine the location of the elder vampires for adv mode, or is it more get lucky enough to stumble upon one and actually survive?
You can check Legends, but it's mostly luck. There should be at least 1 per major city still alive though.
is there a changelog somewhere?
I really wish I'd made a formal one, but no. I'll start one once the new DF version is out.
They can still kill each other even with the 1/1000th material force thing? Dang.
The reason I think the "attacks that are strong against own kind" thing would be useful isn't because they need to be more powerful but that their natural attacks should be useful compared to their manufactured attack, and that suddenly your victim could get a hundred times as large and twenty fives as strong because you attacked using your natural weapons instead of your masterwork weapon.
Just use Shift+A if possible and don't bite. The attacker should still have the advantage in that situation though, assuming you play it smart.