Good thinking to let the regen finish. Turbos usually fail because the oil feed pipe to the turbo bearing and oil return pipe from it get choked with carbon, reducing the lube oil supply. The turbo bearing oil seals can also fail. Oil seal failure is the most likely reason for your smoke and for the repeated regens to get rid of the soot in the DPF. This is why you are advised to idle a hot turbo before switching the engine off. I doubt that condensation on the ECU is connected. Your engine is highly susceptible to EGR clogging and it's difficult to get at, which is part of the reason for the high replacement cost.