Am i right to feel violated, is this ual abuse?

Violated and abused? No, but you do have the right to feel somewhat offended. Your intention and understanding that the session would not be ual was impossibly naive after arranging to stay the night, and body painting when there were no other people present. He changed the conditions without your consent by not having a group there, and that point right then, when you discovered that it was only going to be him and you, was the point when it should have been completely obvious to you that it was not a purely artistic session. No reasonable person could think otherwise, and you should have stopped events immediately to talk about what your expectations for the session were. Since you did not, you bear half the responsibility for what happened.