Which part of Eastern Europe did Iranian languages reach?

Ukraine, Eastern Romania, Southern Russia.

Have you actually sat down to compare the areas of South Asia ( India, Pakistan, Bangladesh, Nepal, Srilanka ) and the area of influence of various Persian empires? Or are you just looking at how small South Asia looks on the Mercator projection?

Area size have nothing to do with my question.

Have you compared present day speakership of the two language groups?

Again irrelevant.

“Just India”. Like South Asia isn’t a landmass of five million square kms or something. Most of which speaks some indo aryan language or another.

70%, but it's not related to my question.