PaulP: "(ENSO is) a standing-wave mode with a fixed spatial configuration"
This claim presumes spacetime is not the more correct notion of space, that standing waves do not oscillate in spacetime, and even presumes Earth is "fixed". Nothing is fixed, in absolute relativistic terms.
Its unfixed "spatial configuration" predicted affecting ENSO sensor buoy data, like the Sun, Moon, and Earth relative positions, plus Earth Rotation and Declination Phases, plus the buoys motions according to sea-state.
Dr. van der Ziel would be an excellent third-party judge of whether Lunisolar Crosstalk Noise expressed in the ENSO data, if he were still alive. You seem unwilling to accept that possibility, despite his classes.
If there is Crosstalk, its a more parsimonious explanation than Forcing. Neither has been shown rigorously, much less measured in proportion, but Forcing involves more complex dynamics than Crosstalk.
NOAA does use an Ensemble Model to study ENSO. Maybe not "best modeled" so, but the same doubt fairly applies to your single Model and all those within the Ensemble. Only LaPlace's Demon, in principle, can compute the best single Model.
If none of this helps, its not for want of trying.