Creative Speculation

You're the hired hit man for the biggest murder case in American history. Are you preparing for the hit and making yourself available to your employers for last-minute changes and consultation? Or are you going to see your wife to beg her to come live with you in Dallas?

None of this makes sense if Oswald is the hired hit man in a conspiracy. Is he not going to do the job if Marina will move the family in with him in Dallas? How does he report that back to his employers? "Sorry, guys, can't kill the President, I'm getting back with the wife, we're moving to Dallas, no hard feelings!"

(Most likely Oswald's intent to kill the president was conditional. This is in no way an attempt to blame Marina, since she could not and did not know what Oswald would go on and do as a result. But it was a pretty shitty thing for Oswald to do. Indeed, I could also see Oswald knowing what his actions would bring down on Marina and their family, and having Marina reject him one last time being a way he could blame her for that part of it.)