You might be interested in Pilot Wave Theory. It tries to reconcile wave/particle duality by claiming there is a real physical particle at all times in an attempt to get around the strange idea of everything being a probablistic wavefunction (the Copenhagen interpretation).

It explains some things pretty intuitively (double slit experiment), but from what I can tell it becomes too convoluted for other things.

Mass can be related to energy with E=mc^2, and you can get some idea of its relation to wavelength and wave collisions.

I think a smallest wavelength is unlikely, because it would put an upper bound on energy. The only side-effect of increasing the energy density (ie a lot of energy in a small space, like a very low-wavelength photon) is the formation of a black hole. I think the question of whether photons (massless) can form them is one of those quantum-gravity issues that are awaiting a theory.