Guns were found to be useless in the armor game, and society didn't exactly seem to be at a great place at that point. Plus there's that weird artifact in joining together, Maybe that did something? And for the second. that can be said for a lot of the games honestly. It's more of a base assumption by the fact it's in the list of "canon" games. Though I will admit I don't recall seeing the magic sword after that. I only placed it where it was because benton is suddenly using a a sword in the ashes. It probably makes sense that this was one of the experiments that happened after the goblin was defeated. but.. Honestly, that felt like a cop out to me to say that since the lack of magic sword was the only justification I could come up with. Plus, benton was originally against the organization and even got rid of 2 of their operatives. They need to reconcile somehow. and the order of events must have to be in that order since bentton first appears in last man.