The holy grail of theoretical physics is the unification of all forces, once gravitation is quantized consistently with the other three.
The behavior of the coupling constants as the energies probed increases gives an indication that indeed weak strong and electromagnetic may be of the same strength at some high energy as the measurements indicate :
The slope at low energies is an experimental fact, and the hope of Grand Unified theories is that they will coincide at one value at the very high energies of 10^16 GeV or so.
The difference between the electroweak sector functional form of the force lies in the self interactions that the strong force exhibits.
The strong force acts between quarks. Unlike all other forces (electromagnetic, weak, and gravitational), the strong force does not diminish in strength with increasing distance. After a limiting distance (about the size of a hadron) has been reached, it remains at a strength of about 10,000 newtons, no matter how much farther the distance between the quarks. In QCD this phenomenon is called colour confinement; it implies that only hadrons, not individual free quarks, can be observed. The explanation is that the amount of work done against a force of 10,000 newtons (about the weight of a one-metric ton mass on the surface of the Earth) is enough to create particle-antiparticle pairs within a very short distance of an interaction. In simple terms, the very energy applied to pull two quarks apart will create a pair of new quarks that will pair up with the original ones. The failure of all experiments that have searched for free quarks is considered to be evidence for this phenomenon.
Tunneling is a phenomenon which can be calculated and a probability given for it to occur. The above paragraph indicates that the probability of a free quark is practically zero, which agrees with observations, and this will include also tunneling, because similar numbers will enter in the calculation.
There do exist papers in QCD calculations where tunneling is considered, but is within the confines of the overall confinement,