And here's the thing, when speaking of "existence in a possible world" that notion is ambiguous. It can refer to both actual existence in a possible world and possible existence in a possible world. Our world is an example of a world with both possible and actual existence.
When speaking of "existence in possible world" it's important to not use the ambiguity of that notion to equivocate possible existence in a possible world with actual existence in a possible world. If that equivocation is made then it can be fallaciously concluded that other existences in possible worlds are just as actual as our world.
When speaking of "existence in possible world" it's important to not use the ambiguity of that notion to equivocate possible existence in a possible world with actual existence in a possible world. If that equivocation is made then it can be fallaciously concluded that other existences in possible worlds are just as actual as our world.