It's very doubtful that whatever ivor has planned is world ending. The Reckoners and their agents don't want to destroy the world, they want to make it so heavily fear induced that they can turn the whole world into a hell on earth Deadlands. Even the penultimate plotline in Classic, the Storm, wasn't really 'world ending' as much as it was linking up the Gomorra plotline to the bigger metaverse issue of the Reckoners trying to screw up things for the Good Guys in even the Hunting Grounds.
As it stands, we're still not that far into the mystery of what's going on with the town's current residents. The Law Dogs/Sloane dust up has really just been a business as usual side show. But it's done it's job of raising the fear level of the town, between having a Whately mayor and acing the latest Sheriff.
So far there hasn't been any major connection revealed between the several items Ivor has collected so far, aside from the Holy Wheel gun and Sabre both being used by Austin Stoker, the Stone Idol and Hoyle's are unrelated as far as we're aware.
Whatever the plan is though, it does seem like the 108 and the Wardens are likely to put a crimp in it between the Righteous Bandits having a 'what's yours is ours' mentality and the Wardens actively on a mission to do some good and clean up Gomorra.
As for which Reckoner this is, I'd say it's hard to put a real finger to it. Gomorra has been a Deadland a few times in the past but even then we haven't seen any direct hand of the Reckoners or any evidence of exactly who they were serving. At least in Classic it wasn't that overt about the Reckoners, we were just dealing with minions and underlings who, even then, didn't reveal their affiliation (Well, we know by now the Lost Angels are under Famine, and the original arc was Knicknevin doing things on his own). I don't think we're going to get a lot of direct action vis a vis the Reckoners, they're big players and Gomorra is still small potatoes by any standard. We'd be more likely to see a servitor make an appearance, like Stone.
I still think 'Sloane' might just be the spirit of the original bandit possessing one of his lieutenants.