Can someone explain the use of "do" here? And is it okay If I drop it and just say: "Agora mais que nunca" ?☺
"do" is simply for adding emphasis to a phrase, to make it a stronger statement. It is entirely optional to add it.
"Now more than never" does not make sense in English, if you think it does then you have been mishearing that phrase. Nunca can translate as both never or ever, depending on the context. Obviously "eu nunca.." would translate as "I never.." but "... que nunca" would translate as "... than ever".
It would be nice if we would have learned by now that "nunca" means both "never" and "ever". However, "now more than never" is accepted as of writing.
It's just a question of double negative I think, not "nunca" translating to "ever." It's a bit like "I have not heard anything" being "I have not heard nothing" in Portuguese (I won't try to write it here since it would be awful). Maybe that means that "nada" can mean "anything" but I think that's misleading. It's just that double negatives are negative in some languages and positive in others.
Interesting theory, but there would only be one negative in that sentence, namely 'nunca'. None of the other words in that sentence have a negative connotation, as far as I can tell (with my limited Portuguese). So the double negative theory cannot apply to this case.
Aside from the fact you're specifying a specific point in time,the basic meaning of the statement is the same..... :)