and note that since the density of Mars exceeds Jupiter's by more than a factor of 2, it occurs within Jupiter's radius, which makes calculation moot. (You could calculate it but the result has no real meaning)

However the calculation of the net gravity experienced by a point particle when Mars is about 185000 km from Jupiter center is easily shown to be zero.

OK you have a pretty basic misunderstanding of what the Roche limit is. You are listing the two cases above as if they are different; as if "the net gravity experienced by a point particle . .is shown to be zero" is somehow different from the Roche limit. However, it is not. From Wikipedia which seems reasonably accurate on this topic:

"The Roche limit for a rigid spherical satellite is the distance,