Honestly;
"Where's the point talking about that now?" Is incorrect. We normally sy "Where's the point in talking about that now?" It sounds more complete.
"What's the point of talking about that now?" Is entirely correct.
"There's no point talking about that now." and "There's no point in talking about that now." are both correct and they both make sense :)
All of these sentences, mean the same thing. They are equally correct and equally polite. However, in my opinion, "There's no point talking about that now." and "There's no point in talking about that now" sounds slightly more rude.
:)