I'm not sure how you got the dipole moment. The uniform component of Earth's magnetic field is only changing the energy of the arrangement, the force comes from the inhomogeneity. As an order of magnitude estimate, the force will be F = B_1 V B_E / (R_E mu_0) with B_1 and B_E being the two magnetic fields, V being the volume of the steel block and R_E being the radius of Earth (as scale of the variation of Earth's magnetic field). mu_0 is the vacuum permeability. Coincidentally, it's comparable to the number you got, 10^(-5) N.

If we don't divide by the radius of Earth we get a (sort of) potential energy, which is tens of joule. Completely negligible compared to hundreds of gigajoule of kinetic energy.