Yes, your first point is the true argument against raising unskilled laborer's wages. The higher their wages are, the more cost-effective it becomes to replace

Yes, your first point is the true argument against raising unskilled laborer's wages. The higher their wages are, the more cost-effective it becomes to replace them with robots. I'd argue that this is probably ultimately a good thing, but many people see it as a reason to avoid raising minimum wages. As for what happens when robots replace engineers, that is essentially the singularity you're talking about. And what happens then is presumably some form of post-scarcity economics (https://en.wikipedia.org/wiki/Post-scarcity_economy https://en.wikipedia.org/wiki/Post-scarcity_economy), though its hard to say exactly what form that will take.