I like this manga but the writing is so ham-fisted. Him stealing the staff was a bafflingingly stupid decision and calling it out as a dumb decision doesn't really fix that. It's clear that they mangaka just wanted him to get really powerful, really fast. I hope this doesn't become a battle manga.
People must be beating the gate guardian and having others rush through the gate with them pretty frequently for there to be an entire city of people. I could believe that there would be small tribes of badasses like the ones they ran into when they went through the gate but for there to be tons...
The boats could be a fake option because the souls that end up in this situation would never take it. Giving them the fake option would increase their suffering because now they think that they missed their chance at a peaceful afterlife.