1). The interference of dipole moment was previously explained, as increasing the permanent Van der Waals forces.
2). The exemptions from the Troutons’ rule were clearly mentioned above, too.
3). Other parameters that interfere in the vaporization enthalpy are also mentined above.
4). Degrees of freedom, etc. reflect on the vaporization entropy Sv, which numerically coincides with the specific heat (or better, the molar heat capacity Cn).
So and up to the phase transition, an amount of heat is consumed in order to reach the boiling temperature Tb and which for 1 mol, is Q = CnTb or else, Q = SvTb.
And then, an additional amount of energy is consumed for the phase transition, which is equal with the vaporization enthalpy and not with the vaporization free energy otherwise, vaporization entropy is counted twice in regards to the overall energy that is needed for evaporation.
This is the same as counting the same cost twice, in accounting.