I admire your tenacity Nachos23 it sounds frustrating. I am following this thread with interest as I am interested in retrofitting the DCT or M3 shifter. Its a bit beyond me so I was looking to purchase the mod. I am not sure if it helps but the guy at the aftermarketbulbshop.com (I think they are a sponsor) said he can do both on an E46.
However although the lights work its still a mechanical shift. So do I understand it right that you are trying to make the PRND electronic as well? I have just bought the paddleshift wheel/mod for the steptronic so I am excited by that but what I would really like is to be able to engage P when sitting at the lights via a button. The P button on the DCT shifter would be ideal so I hope you get it working. I have asked a couple of people whether they can do it but no success yet.