1). You are right!

Your calculations are correct. I was wrong and strict. So, I fully apologize for this.

2). Coming to the point:

Imagine that you have a combustible that has a theoretical combustion heat = -21.93 kcal/mole. But during combustion an endothermic reactions occurs, which consumes +10.00 kcal/mole but the reaction product is also combustible with combustion heat = -17.17 kcal/mole.

Neglecting their molar ratio for simplicity reasons, the overall combustion heat is:

-21.93 + 10.00 - 17.17 kcal/mole = -29.10 Kcal/mol

Thus and in terms of thermal yield: |29.10| > |21.93|

But in terms of Hess law: -21.93 > -29.10

3). Something similar happens hereby:

On the one hand, sulfur consumes (unknown?) energy, in order to keep a planar molecule but on the other hand, the planar structure contributes to the stabilization of the hybridization and the aromaticity of thiophene.

4). Restarting from the beginning:

The hydrogenation enthalpy is an approximate method for the calculation of aromatic energy, which has a high scientific and educational value. This method may work with benzene but it tends to be inaccurate with heteroaromatics, fused and polynuclear aromatics, aromatic ions, as well as with aromatics that have a number of members that is different than 6 because it does not take into account the size of the heteroatom, neither the difference of ring strain between the aromatic rings and their perhydro-derivatives (note that 6 members rings have ring strain ≈ 0).

More accurate results can be taken by using specific quantum equations, which are specially invented for.