How did he get out?

He was contacting the mothership. And they responded!

He didn't. He collapsed near the upper right lamp post.

Walked sideways

He walked diagonally to the top left, you can see the footprints

he walked all the way backwards

Following the same path, but backwards.

Just stepped in his foot steps not that hard to figure out

ocd goals

He did what the alcoholic from Tremors did...