Spoiler:I agree with those who think Wolfgang did it of his own free will. He sent Gabriel away so that he wouldn't stop him from doing that. It was a great sacrifice but he had also been talking about how he felt he didn't do enough as a Schattenjager and I think he felt it was his duty to do this. And I also agree that Gabriel was cursing out Tetelo because all the events that led to the sacrifice were because of her. Plus it's her fault that a heart sacrifice was needed to get into the circles.
As for the mummies:
Spoiler:I had no problem getting past any of them. I just simply kept going through the doorways, even when one of them was standing right next to it, and they never got to me!
