AOA,
Personally I think you should re-join NADRA once again..... as CSS is a game of luck and no one can predict your luck.
Second, I would like you to try for CSS 2008,(you can do it with you job, as I know many people who did CSS along with their job). If you're selected for DMG, PSP or PFS(if you wish, I, personally, being a research living in Europe, don't like PFS), then go for it. You can pay some money to NADRA(for which you have signed a bond with them) or you can go to a court against NADRA(as writing a bond is equivalent to bonded labour). I think DMG and PSP are worth joining.
But if you are selected for, say, IC, CE etc, then don't leave your luxurious job as you can do no good to the nation in these cadres nor you will enjoy that much as you enjoy now in NADRA...................

Decision rests with you,