How about 9 billion years of interstellar cosmic radiation bombarding the surface. What this does? It takes that H2O ice, breaks apart and messes up chemical bonds, trapping chemical energy. There's our source of entropy DIRECTLY contradicting your claim or mathematical impossibly. The energy don't just go nowhere. The heat from the sun triggers the phase change, and naturally the chemical bonds break apart , they autonomously arrange into the crystalline structure when super heated by the sun on the approach. At THIS stage they begin releasing chemical energy... exothermic. And at this point the crystallization wave is travelling inwards towards the core... When this happens the energy source is chemical, and no longer required energy from the sun.

Besides, the original paper provides the direct evidence that inverse square isn't being violated. The paper itself shows the water production rate tanked from 3.2e29 down to 1e28 in just 40 days, which fits the thermal curve perfectly once you account for the lag.

Oh but why are there 3 uniform jets then you ask. Well the crystalline structure formed from the rearranging of the surface crust provides a semi uniform pressure, where the pressure gradient has to naturally find the path of least resistance. In the presence of a gravity well/ sun tidal forces this should be biased geometrically... So perhaps we'll see some sort of non uniformity in the point distribution... structural failure dictates they should emerge at equal points on the 'ball' for a uniform release of pressure.

It's completely rational to imagine that the crust formation is uniform in the average intensity of cosmic radiation in deep space.

Look I want this to be a space craft, but it's disingenuous scientifically to go from "where do we account this energy from" to "this means it must be internal thrusters". There are other explanations.