How can the Higgs have so many different Yukawa couplings? How can the Higgs have so many Yukawa couplings?  Isn't this about the same as saying the Higgs has a force or charge for each different coupling?  Is this some indication of substructure for the Higgs or some kind of mixing with other scalar neutral particles that have not been found yet?
 A: It has different yukawa couplings with all of the fundamental particles because this is allowed by the symmetries of the standard model, and if this were different, the standard model wouldn't accurately predict physics.
Whether some theory that envelops the standard model will have a way of predicting the yukawa couplings is, of course, an active area of research.
A: The Higgs particle and the Higgs field do constitute a 5th force - in addition to the nuclear (color force), the electric, the weak and the gravitational force. The coupling to each particle becomes the mass term for that particle due to the non-zero value of the Higgs field.  As Prof Matt Strassler says (in http://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-known-forces-of-nature/the-strength-of-the-known-forces/ ):

The Higgs Force!?
As of 2012, we have a new force to think about: the force between two
  particles induced by the Higgs field! This is not to be confused with
  the effect by which the Higgs field gives the known elementary
  particles their masses; the Higgs field can do this to a single,
  isolated particle. That’s not a force; it doesn’t push or pull.  But
  the Higgs field can also induce a force between two particles; this
  happens in much the same way that electromagnetic forces are created. 
  However, as far as its effect on ordinary matter, this force is very,
  very hard to detect.  At short distances, for particles like electrons
  and the up and down quarks that dominate the proton, the Higgs force
  is very weak (much weaker than electromagnetism, but much much
  stronger than gravity).  At long distances, like the weak nuclear
  force, the Higgs force becomes extremely weak, because the Higgs
  particle, like the W particle, has a mass.
The Higgs field induces a force similar to the weak nuclear force in
  that it has a very short range, becoming ineffectual at distances long
  compared to ℏ c / Mh ~ 2 × 10-18 meters (1/500 of a proton’s radius),
  where Mh ≈ 125 GeV/c² is the Higgs particle’s mass. And at first
  glance the formula is similar to that of gravity, in that it is an
  attractive force proportional to the masses m of the two elementary
  particles being attracted.
  
  
*
  
*αHiggs = (mc2 /4 π v)2  × $e^{-Mhr/ℏc}$  --(for r »  2 × 10-18 meters) 
  
*αHiggs = (mc2 /4 π v)2    --(for r «  2 × 10-18 meters) 
where v = 246 GeV is the constant value of the Higgs field found throughout
  the universe. [Actually, if one is careful, there is an extra square
  root of 2 in there, but let's keep the formulas simple-looking.]
Be cautious!  The resemblance to gravity is misleading. This formula
  is only precise for the known elementary particles — those objects
  that get their mass from the Higgs field. It works for electrons and
  muons and quarks.  It is not correct for protons, neutrons, atoms, or
  you! That’s because a proton’s mass (and a neutrons, and therefore an
  atom’s, and therefore yours) does not entirely come from the Higgs
  field. This is in contrast to the formula for gravity, which is
  correct for all slow objects! Instead, for ordinary atomic matter,
  we’d have to replace the formula with one that looks similar but has a
  different factor in front, slightly different for each atom.
  Qualitatively, however, the dependence on the distance would remain
  similar.
Also, the formula I’ve written also assumes there is only one Higgs
  field and one Higgs particle (which we don’t yet know to be true, but
  is the simplest possibility consistent with current data.) If that’s
  not the case the formula will become more complicated, while remaining
  of a similar form.
  
Fig. 2: The relative strengths (α) for each force, as a function of
  radius, between about 1/300 of a proton's radius and 30 proton radii. 
  Fig. 2: The relative strengths (α) for the forces acting on a top
  quark and top anti-quark, with mass almost 200 times larger than a
  proton, as a function of radius, between about 1/3000 of a proton’s
  radius and 30 proton radii.  The Higgs force and the weak nuclear
  force become extremely weak at distances even smaller than the proton
  radius, while the strong nuclear force becomes strong at the proton
  radius. Electromagnetism stays moderately weak at all distances. 
  There are subtleties, ignored here, involving electromagnetism and the
  weak nuclear force at sufficiently short distances (grey box). Gravity
  is incredibly weak and lies far below this graph.  For the up and down
  quarks in the proton and neutron, the graph would be similar, except
  that the Higgs force would be far too small to appear on the plot; the
  same would be true for two electrons, though it is unaffected by the
  strong nuclear force. 
How strong is this force? Well, at very short
  distances, shorter than 2 × 10-18 meters, the Higgs force between two
  top quarks is comparable to the strong nuclear force at that distance
  (see Figure 2)! But for electrons, which have a low mass because their
  interaction with the Higgs field is small, the force even at  short
  distances would be much weaker than electric forces — more than a
  thousand million times weaker — though still thousands of millions of
  millions of times stronger than gravitational forces between
  electrons. Yet if you consider two electrons in an atom, which are
  about ten million or so times further apart than 2 × 10-18 meters,
  then the Higgs force between them is much, much smaller even than the
  tiny gravitational force between them, as it is suppressed by
  e-10,000,000. [Even if the Higgs field did give protons and neutrons
  all their masses, the Higgs forces inside a nucleus would still be
  vastly smaller than those of gravity, which in turn are incredibly
  small compared to the residual strong nuclear force that holds the
  nuclei together.]
It is the incredible weakness of the Higgs force in the context of
  ordinary matter that makes it so hard to discover. On the one hand,
  the Higgs force, like gravity, is always attractive and can’t be
  cancelled.  But on the other hand, that’s irrelevant, because, like
  the weak nuclear force, the Higgs force does not survive to long
  distance, because the Higgs particle, like the W particle, has a mass.
  The Higgs force at ultra-short distances is much stronger than
  gravity, but at nuclear and atomic distances, it is much weaker,
  because of the Higgs particle’s mass. And for the low-mass particles
  out of which we’re made, which interact weakly with the Higgs field,
  the Higgs force is always thousands of millions of times weaker than
  electric forces, even at very short distances.  So even though every
  atom in the Earth exerts a Higgs force on every other atom in the
  Earth, that force is so incredibly minuscule, even for neighboring
  atoms, and especially for distant ones, that it has no detectable
  effect.  This is why we had to go find the Higgs particle directly to
  confirm the Higgs field exists; we couldn’t just go looking for the
  force it creates, the way we can use the observation of electric and
  magnetic forces to confirm that the world has electric and magnetic
  fields.
When might we actually observe this new force? It’s effects will first
  be observed either in the scattering of W and Z particles off each
  other (which will eventually be done, indirectly, within the
  proton-proton collisions at the Large Hadron Collider) or in the
  interaction between a top quark and a top anti-quark (which can be
  observed at an electron-positron collider — in fact I wrote my first
  particle physics paper [see in particular Figure 11 of the paper]
  about this very phenomenon.)

