Based on what you just said, the simulation "argument" is no argument at all. The three propositions cover all possible cases. How can you argue against that? What would be the counter-argument?
The counterargument would be simple: a counterexample where all three propositions are false at the same time.
The Simulation Argument is really a tool, and a challenge. It sets things up such that, if we manage to disprove 1 and 2 empirically, we get stuck with a shocking realization about the basic facts of our existence. It gives us an unusual way of indirectly testing whether or not we are living in a simulation. That's a lot out of something that "isn't an argument at all".
> The Simulation Argument is really a tool, and a challenge.
No it isn't. It is Pascal's Wager updated for the 21st century. The only way it can be "proved" is if we are living in a really bad, poorly maintained, fundamentally broken, cheaply outsourced simulation.
