CP violation

While reading some stuffs related to neutrino oscillations, I realized that neutrino oscillations can happen only after Electroweak Symmetry Breaking (EWSB). Since before EWSB happens, neutrinos( in fact all leptons and quarks) are massless and hence there is no oscillation and thus there is no CP violations. I started wondering about the cosmological significance of the CP violation in the leptonic sector. According to Shakarov's criteria CP violation is a must for leptogenesis to start. Now if the CP violation we see in the leptonic sector has something to contribute to leptogenesis then EWSB must happen before leptogenesis started. But according to current understanding of the thermal history of the Universe the matter-antimatter asymmetry started long before the Gev scale (EWSB). Thus whatever CP violation is there in the leptonic sector has no contribution to the leptogenesis. Although I have very little knowledge in leptogenesis, I found this point interesting. I asked my supervisor regarding other sources of CP violations which can contribute to leptogenesis. Then he said right handed heavy neutrinos is one such source. I have seen many models with B-L extended gauge symmetries which can accomodate right handed neutrinos. Now there are certain things which are not clear to me:
1. Why right handed neutrinos should preferentially decay to leptons rather than anti-leptons. I want to know how the CP violations take place in this case. Its definitely not like the oscillation of leptons which gives rise to CP violation in the usual leptonic sector.
2. Is it true that total lepton number is violated in such decay of right handed neutrinos? If yes then how can we incorporate these lepton number violating interactions in B-L extended gauge models where B-L breaking scale is not as high as the scale of leptogenesis.
I think I need to do some more careful studies rather than blindly coming into any conclusions. If anyone can help me with some references or comments that will be highly applauded.