Upload & Sell: Off
The cast doesn't look like a Lee Big stopper. Maybe a B+W or Hitech? I use the B+W ND110 and I usually just mess with the WB. Since you have the non filtered shot as a references you can also mess around with WB, sliders, etc to try and match it as close as possbile. Photoshop CS can be a good tool for that. Also sometimes I'll use one of the filters in Nik CEP4, which can be helpful.
As far as your shots I like #3 the best besides it being a litlte underexposed IMO. Some adjustments in curves/levels could help it too. If you have a cable release I would have tried a longer exposure, 60 sec, 120 sec or even longer.