Damn, this story is amazing, and the slightly monotone voice in which you tell it - which may or may not be a conscious decision to apply - works really well with it. The production could use some loving: the volume is kinda low, some EQ and a minute touch of reverb would add some sparkle to your voice and the background noise is an undefined rumble - either try to get rid of it or make sure it has definition. As for the storytelling itself, I don't think you need to actively put on another voice for your different characters, but if you don't, slightly longer pauses between their lines would help differentiate between them.
If you ever have another story like this one and polish it up like that, you'll have certified grade A material on your hands. Keep 'em coming!