So, let's see what we have here:
Conclusion? As several scans you posted: Leorg used the demon king of tirany, Avos Dilhevia as the origin of his magic. Risked his life because he used the wrong name of the demon King, and such magic didn't affect Anos because it was the very origin of the magic.
Your interpretation of "Since he used the name of Avos Dilhevia, then the origin was Avos Dilhevia instead" takes too many assumptions and contradicts many statements. So, let me ask you the following questions:
Why did Anos state he didn't feel nothing because he was the origin of the magic if he supposedly didn't feel anything because he was too strong?
Why did Anos reiterate he was the one used as the origin of the magic (but with the wrong name) once he knew that his name was confused by Avos Dilhevia?
Why did all the magic caster endanger their life (something that only happens if you call the origin you're using by the wrong name) by using the origin of the Demon King of Tiranny if, according to you, they're not using Anos as an origin, but other being which is truly called Avos Dilhevia?
Short answer: Because the origin of the magic is neither Levi with the fake name of Avos Dilhevia nor Misa, who obtained such name because the rumors. The origin was, as stated many times by Anos himself, Anos. But with a wrong name