Why does this kanji use "sora" as its reading? There's a song called and it's read as "Hekira no Sora e Izanaedo". Is "Sora" another reading for I don't see it listed on Jisho.org, and seems to almost always use "Ten" as its reading.

The reading of is a nonstandard reading found almost exclusively in crative writings such as lyrics and novel titles. It's in the same vein as this. Using a nonstandard reading is a common way to make the name sound more interesting in Japanese.

In person names, there are a few people named (including this seiyu), but I think it tends to be used as a little peculiar stage name.