A single photon has an associated electromagnetic wave. The wave is spread out in space, but the photon is considered a point particle. If the photon is absorbed, the entire wave disappears. Photon absorption is instantaneous, so the wave disappears instantly. In other words, the wave can no longer be detected anywhere in the universe; despite that the interaction happened at a single point.
Is my understanding correct, and if not, what am I missing?
Light, a classical concept, emerges from zillions of photons in a continuous mathematically demonstrable way, but photons, a quantum mechanical entity, are not light.
At the quantum level photons are mathematically connected to the frequency of light with a complex wavefunction, a solution of a quantized form of Maxwell's equation, that is why it can be expressed with the average E and B fields it may build up when assembled in bulk.
and its $Ψ^*Ψ$ , as all quantum mechanical solutions, represent the probability of finding the photon at an (x,y,z,t). So the individual photon is not spread out all over space time, it has a probability of existing in space time points given by the solution.
You are missing that the wave nature of a single photon is a probability amplitude, not an energy amplitude. Once and if you learn quantum electrodynamics here is a link on how the classical emerges from the quantum probabilistic level.
You are not correct and you are not incorrect. This is the realm of quantum interpretation, and this particular conundrum is called the Einstein bubble paradox. What exactly is happening down there is an unresolved question. All we really know is this: light propagates according to classical electromagnetism, but its energy and momentum can only be emitted/absorbed in quanta. Make of that, philosophically, what you will.
