I think the cast had known for a long time and were just not allowed to say anything until the press release. Most of them would have gotten over their shock a long time ago.

I agree with you, at least for the first season. The plot is fairly straightforward and could have been easily streamlined while only making small cuts and changes While there were obvious large changes to the characters that I didn't agree with I think one of the main things that derailed the series was making the Aes Sedai such a huge component of the season. In the series the Aes sedai start off as this mysterious organisation that is not fully trusted. It is not until the girls go to train we meet them to a greater extent and We realise how out of touch ad self centred most of them are.

This really depends on where you live. In many places this is very common and noone bats an eye at a two year age difference.

I think they should have started with a brief telling of the history of the breaking via voiceover and some random scenes. Explain the drilling of the bore, the war of power, The 100 companions sealing the bore and the backlash of the taint then Lews madness and the breaking caused by the men. It doesn't need to be long or detailed but it would give enough background to aid the audience in understand what is happening.