I'll try and answer these questions from memory as I currently do not have access to Pose2Lux or Luxrender, having decided to go kayaking in Wales for a few days!

Anyway, yes - Pose2Lux will use the lights from your Poser scene. You can configure them further in P2L, and assign them to groups. Lights assigned to the 'ignore' group will not be exported to Luxrender. If you name the lights in Poser in the style of groupname:lightname then the light will automatically be assigned to the specified group, so you could (for example) make a light in Poser with the name ignore:light1 and it would light your scene in the preview window but be ignored by Lux - this can be quite handy!

IDL is a form of global illumination (GI) and as such is similar to how most of the Lux Surface Integrators work. The default Surface Integrator is 'Bidirectional' and that uses GI.

There are two ways to use a skydome in Pose2lux. One is to set it up as an emitter and then choose appropriate wattage, gain and efficiency settings for it. Better (in my opinion) is to assign the 'Skydome' material to it and let P2L sort everything out for you. The latter approach only works if you use a skydome which is a complete sphere with an appropriately mapped image (such as Bagginsbill's excellent free environmental sphere).

Free stuff @ https://poser.cobrablade.net/