I don't think he meant "reward" as material, but that he had earned Jesse's trust. Like, I'm the only one he told his secrets to.
I thought it was pretty obvious. Idk how you can read it as a material reward after all we've seen. His reward is to be indespensable to Jesse. Whether that means gaing his trust or holding a dangerous secret hostage we don't know. Law is a little crazy after investing all he has in Jesse. Feelings, dignity, his freedom, his future, all poured into Jesse. He wants...no he needs to have his "investments" returned. With devidens.
No matter how twist this story may seems, Jesse still trusts Law a lot, even with his life, I would say.
I remembered Law explained that there must be someone in the Moritat who knew that they were in the virtual world. Without this person, the other people will not be able to come back because they wouldn't know it was not reality.
The fact that Jesse trusted law to be the key person means that he had entrusted his life to Law. If Law did not tell him the truth, Jesse would have been trap there forever.
So yeah, over all, I still have hope for the couple. I'm a sucker for happy ending. :D So please let it be a happy ending. Fingers crossed.ヾ(☆▽☆)
I was hoping he won't kill her, but when he did, "Oh well," was my reaction.
Just like Bum, I didn't really feel much. Too bad, their fates are likely to be death or prison.