Is there a way to use enviroment mapping on Objects in P5?

Depends upon your definition of environment mapping. If you mean dynamically creating reflection maps based the object's surroundings, then no, as far as I know Poser has no shaders capable of doing this. It does have a sphere-mapping shader, but you'll have to provide the reflection maps yourself. And there's a raytraced reflection shader, of course.

Does anybody of you have the right settings to simulate Latex Clothing?

Latex is usually tight-fitting, whereas the Cloth Room is better suited for loose, flowing fabrics. But I believe someone conducted some experiments with scaling clothes down in the Cloth Room to make them tighter-fitting, shortly after P5 was released.