The f stands for the rotational component of kinetic energy, which is 1/2I(w^2), where I is the moment of inertia for a solid sphere, which is 2/5m(r^2). Since there is a '1/2' at the beginning of the line, the 'f' in the formula is '2/5'.
You have not taken into account the vertical translational energy in the parabolic trajectory after it leaves the table.
When you calculate the horizontal speed as 0.38m divided by the 0.419s (I assume) taken, then this is an average velocity, and in the horizontal direction, to assume that this is the same as the final velocity is probably ok (since air resistance will be low).
However, in the vertical direction the final velocity will be twice the average velocity (again assuming low air resistance). This will be where a lot of your missing energy has gone to.
Finally, since the marble drops a total distance of 'h + H', the potential energy available is m.g.(h+H), which will make the starting potential energy calculation a lot higher, and your missing energy even higher !
OK, for an object falling from zero vertical velocity, then the time taken to fall through 0.865m under gravity will be given by the usual s = ut + 1/2a(t^2) formula, which gives a time of: sqrt(0.865*2/9.81) = 0.420s. This tallies with your 0.419s measured.
And so ... the energy released from the fall in the marble's position in the gravity field is given by: m.g.(h+H) = 0.0049*9.81*(0.089+0.865) = 45.86mJ.
... the rotational kinetic energy is given by k.e(rot.) = 1/2.m.(v^2).2/5, and assuming negligible loss in horizontal velocity due to air resistance over the fall to the ground, this is: = 0.5*0.0049*((0.38/0.419)^2)*0.4 = 0.806mJ.
... the translational kinetic energy at the end of the fall is given by using a distance travelled which is the diagonal magnitude of a right-angled triangle with sides 0.38m and 2*0.865m (the 0.865 is doubled because the instantaneous velocity will be twice the average), which is: sqrt((1.73^2)+(0.38^2)) = 1.771m. And so the kinetic energy is the usual 1/2.m.(v^2) = 0.5*.0049*((1.771/0.419)^2) = 43.770mJ.
So, compared to a potential energy release calculation of 45.86mJ, the kinetic energy gain is 43.770 + 0.806 = 44.576mJ.
The difference is 1.284mJ or 2.80% of the potential energy released ... which is close to a more realistic figure for a loss of energy due to friction on the incline and air resistance on the incline and on the downward fall.