DominicCobb said:

I get leaving out stuff like the identity of his father for a sequel, but simple stuff like his feelings about leaving Earth behind I think is rather essential to completely understanding the character.

Throughout the film they give lots of hints about the resentment he fills about being torn away from his family.

Again, we're just meeting the character in this film. If they were to give everything away in their first go there wouldn't be anything to explore about the character later on.

My biggest issue with that scene is actually his slave girl and what she does which I found totally random (though again I understand that they wanted to show the power of the orb, but still this was not the best way to do that I think).

Earlier in the film they show how cruelly he treats his slaves. In the scene in question, he just got done explaining how the infinity stones bestow awesome power to those with the ability to wield them. Overhearing that and no longer wanting to be enslaved and at the mercy of this psycho she makes a play to escape. I don't get what's hard to understand about that.