1) Yes, you can turn off shadow casting BUT not for individual lights. You can stop any MESH casting a shadow by including the flag "lb_noshadow" in UserFlag1. Check the Manual -> Reference section near the top (I think).
2) J is right. You'll need to add the 'backfaces' in your modeller.
3) Very large single polygons are not a problem - there's actually a setting in there to deal with them (PreScale). I use VERY large scale geometry myself and LightBulb just loves it! Just make sure you don't set the LumelSize too low, and increase PreScale if you experience 'artifacts' in the lightmap.
Hope that helps you make your decision :)
2) J is right. You'll need to add the 'backfaces' in your modeller.
3) Very large single polygons are not a problem - there's actually a setting in there to deal with them (PreScale). I use VERY large scale geometry myself and LightBulb just loves it! Just make sure you don't set the LumelSize too low, and increase PreScale if you experience 'artifacts' in the lightmap.
Hope that helps you make your decision :)