[lisper]

I'm not a "real quantum physicist" but I've been studying QM as a hobby for thirty years. Your intuitions are not far from the mark. What you call "becoming intertwined" is a real physical phenomenon called entanglement. The problem with your definition is that there is no "point" at which entanglement "happens". The creation of entanglement(s) is a continuous process, not a discrete one, so the transition from "unmeasured" to "measured" on this view is also continuous. This process in the aggregate is called "decoherence" and it can be described very precisely, and it correctly predicts all of our observations, including the fact that all macroscopic observers will agree that either the cat is alive, or that the cat is dead.

The problem is that nowhere does the math say that the cat actually is alive or dead. Again, mathematically this is a consequence of the fact that the Schroedinger equation is linear, so if you start with a superposition of states, that can only evolve into another superposition of states. The math says unambiguously that the cat and all of its observers are in superpositions. In order to extract a single privileged objective classical reality you have to add some additional mathematical constraint, and no one has been able to figure out a way to do that that isn't either ad hoc or at odds with the data.

And it gets even worse than that because of the Bell inequalities, but that's a whole 'nuther kettle o' worms.