Here's another way to think about the location of the big bang.

If we look at the night sky, between the planets and stars, into the darkness we find there's a faint glow emanating from everywhere. This is the cosmic microwave background, the oldest electromagnetic radiation that has taken the longest possible time to reach us because by this construction you avoided all the other objects in the way. This extends your view of the past to its maximum value: the age of the universe, which is literally all of the available time for photons to travel. Note that this is a simplification because it makes some assumptions about the transparency of the early universe, but it suits us fine.

It's coming from everywhere because all of those places were there at the big bang. Where was the big bang? It was over there. And also in the opposite direction, there. Because all of those places were here.