Well, I never understood, queeq, why you think Vader's seriousness would prevent him saying that line. That argument makes no sense at all, he is in no way trivialising things. I repeat, as the pupil of someone who does not beleive in luck, what else WOULD Vader say of someone he thought was having a good day? 'The Force is strong with him', of course.
Meanwhile, when he said 'the Force is with him' about Obi-Wan, this was a remark on his competence, and on how Tarkin's cronies certainly wouldn't be able to deal with him.
When talking about Luke, they are simply talking about how powerful he actually is with the Force. They don't ALWAYS have to mean it figuratively! Stop being so literal, queeq, it's all on context. ALways seemed pretty clear to me.
So your opinoin is very humble indeed, queeq, because you have- again- said nothing that fundamentally negates any of my points.