The entire city was driven insane by an Eldritch AbominationThe tentacles that we see trying to escape from The Plague's basement are Cthulhu's tentacles, and since he lives near the town where the movie takes place, he drove all the residents there insane. This would explain Hope Town's ludicrous, Up to Eleven amounts of depravity.
The Hobo's name is Bear.Hence his love of bears and his random bear facts, as well as basically being a bear as his story showed.
The Plague is Daft Punk.
The Hobo gets his ammo from the people of Hope Town.Those who supported his vigilantism but didn't want to incur Drake's wrath by openly helping him would buy shotgun shells and leave them out in public places for him to find, which is why he never ran out.
Ivan was killed because Drake owed the Plague.Nick Bateman voices both Rip and Ivan...
The Hobo never existed.Abby and the decent people of Hope Town finally got fed up with Drake and the corrupt police force and began fighting back. The Hobo story was only a story passed around to create a heroic figure for the people to rally behind as they took back their town.
The hobo is a long walk judge during the atomic wars.The hobo was a judge from the early years (during the timeline of Origins) but before the bombs nuked America and Canada into the Cursed Earth. The hobo left for unspecified reasons (perhaps mental illness, which is why he can't remember) and was one of the earliest judges to take the long walk option. Order was breaking down across America, resulting in the city we see the hobo wander into. He wasn't sure about taking law to the lawless until he has to choose between the lawnmower and the shotgun, when his training and experience kicks in.