Dear khaled
It's possible moisture has been drawn into the system via the leaking distributor. The oil discolouration has most likely occurred due to this ,plus due to the long brazing process ,flux, oxides etc, which have been washed back into the compressor sump.
Replacing the oil and fitting good quality filter driers should flush the system.
Regarding the flooding back issue ,you say you replaced the TEV power assembly ,but what about the orifice,as the seat may have become "wire drawn" due to dirt or flash gas when the unit had been running short of gas due to the leak.
Suggest fitting a replacement orifice and re setting the orifice spring to allow the TEV to operate with a reasonable superheat around 5k ,also check the tev bulb is fitted tightly to the suction line making a good contact, with a light wrap of insulation material over the bulb to prevent surrounding air movement affecting the bulb function. If possible a couple of pictures of the expansion valve and distributor and position of the bulb and equalising line will help us to advise you, also details of the TEV installed
.All the best Glenn