It's not clear to me why you're allowing the possibility of an upper-tier universe. In particular, a similar kind of example to one you give suggests that it's not meaningful to talk about being in a sufficiently good simulation.

Suppose we're wondering whether we're in a simulation or not. But there are a couple of possibilities. In one of them, the alien simulation-runner's mug of coffee is green, and in the other it's blue. But both of these situations have (to abuse notation somewhat) the same causal arrows pointing into our experience, and so we can't meaningfully talk about them (if I understand your argument).

That reminds me a lot of Putnam's argument that we can't be "brains in vats", which also proceeds from similar thoughts about reference. (The above is a butchered translation of it!) I'd recommend reading it if you haven't - it's not the clearest thing ever, but he's riffing on the same themes. But I think the conclusion tells against the argument: we surely can talk meaningfully about things like being "brains in a vat".