I totally agree with you that they should have asked the PM to step down so as to proceed with the investingation though internationally a PM would have resigned anyway if two of the judges had declared him dishonest.
However, I disagree with you that NS didn't know about the verdict in advance...there is plenty of evidence that he knew it already and even some journalist knew that it was initially 3-2 and then it got swapped i.e. 2-3 in the very last days and I think it was due to the establishment intervention.
Remember judges alone cannot do anything. They need institutions to obey their orders and execute them. If the establishment is not supportive, the judges will talk a lot but won't be able to do anything. And establishment was perhaps affraid of a sudden change and some hypothetical unrest because let me say that a visionless coward is leading the establishment.
Since I have been reading about the history of Pakistan and different verdicts by the supreme courts, I found out that Justice Sajjad Hasan Shah was about to give a verdict against NS, but then COAS, the shameless, the unmanly Jahangir Karamat did not support the SC rather decided to stay neutral and leaving the SC open to the attack by NS goons and ousting of the justice through supreme judicial council which was purchased for a hefty amount and the guy lanati bearded ugly person who brokered the deal was Tarar who was later made president of Pakistan as a reward.
NS later disposed off and scrapped the unmanly Jahangir Karamat. That is why I like Pervaiz Musharraf that at least he showed the courage and boned NS when he tried to discard him. Though even he compromised and knelt down before KSA otherwise he could have at least tried NS for corruption charges and disqualified this whole family through the SC and banned them for politics forever and recovered all the wealth they stole.
The silver lining in the current murky situation is that these judges have not accepted any money and they are finally going to disqualify him. But the most positive thing is the independent media that has provided the people of Pakistan up-to-date information despite the fact that govt has purchased quite a few media houses and the anchors. And this has changed the whole dynamics and despite NS doing his utmost, all of his actions are getting backfired and rendered useless. Futhermore, the Dawn fiasco has put so much public pressure on the unmanly establishment that they will have to support and execute the verdict otherwise they will lose all the public support and even there might be a mutiny within certain insitution because there is a considerable seething anger in the lower to even upper ranks and head of the institution had to face quite a lot of critical and hard questions. The nation is far more aware than 1990s and a leader like IK is leading the opposition.