Like I said, I don't feel that confident talking about screenwriting but ...
There is one thing I can say with absolute certainty:
Never, never never start work on a film (or a book) without having a title. You will never get a good title once shooting has started. There's a reason for this. Before you start work you're full of hope, aspiration and excitement - as in the early days of a love affair. You're full of poetry.
Thinking of a title after the film is made is like asking someone...