7. You essentially answered yourself in question 6.

P4's light algorithms aren't very precise.

10. williamsheil gave lightType 2 a try.

The result is a "local" light, a hybrid of Poser's infinite light and spotlight. It illuminates the entire scene like an infinite light, but creates shadows only within a narrowly-defined field, like a spotlight.

Here's the relevant thread:
http://www.renderosity.com/messages.ez?Form.ShowMessage=645709