It was a bizarre scene. It was also a bit vague and I couldn't make heads or tails out of the scene.

They leave it up to the audience's imagination. I think they certainly got intimate in some way or another, and it was in a way that made Nina uncomfortable. Their conversation in the mexican restaurant heavily implies that he was coercing her into sexual acts that she didnt want to do.

I think he did. We see how messed up both characters are as the film progresses. They probably had sex at one point since at the end Nina was practically all over him. She pegged me as the type of person who needed to have some form of power, or be in control, while he was just a user of people, and would hold the video footage over her head to convince her to do things she didn't want to.

Definitely. Lou had a read on her and had her alone in his apartment on the understanding he wanted her sexually.

Plus, that was before she got visibly aroused by his last two triumphs caught on camera. Lou had it all!

A great rags to riches tale!