This is, actually, a very good summary of the situation, Cassandra :)
Let me add two things:
1. Yes, President Duda refused to swear the PO-nominated judges in - and it's important to realize that he had zero right to do something like that. The law and the constitution don't give the president any say in the process of the selection of the Tribunal judges. The parliament chooses them, the president is obligated to swear them in. Duda's refusal to do so may well be a case of him openly breaching the constitution.
2. Yes, the new parliament (which PiS has majority in) annulled the the previous parliament's choice of the Tribunal judges - and again, many commentators say that it's actually an act that violates the current laws in that matter. Many commentators say that the parliament just cannot execute a move like that, that annulling the judges' nominations in such a way is illegal.
3. There was a new development this Friday - this time, it's the government that quite probably violated the law and the constitution. Basically, for the Tribunal's ruling to come into effect legally, it has to be printed in this special government publication. Aaaand... it seems that the government is actually sabotaging the printing of the ruling that says that the three of the PO-nominated judges should be sworn it. The ruling came on December 3th and it still has not been printed. At first, the government wasn't commenting on this - but, on Friday, the minister that's responsible for these things sent an official letter to the Tribunal saying that she decided that the ruling is invalid (because of some formal excuse) and she's not going to print it unless the Tribunal provides explanations. And again, it's a case of PiS officials making something they have no right of doing: the Tribunal's rulings are considered final and uncontestable, the government is obligated to print them. Meanwhile, the government seems to be openly contesting the Tribunal's ruling, trying to stop it from coming into effect.
What all of this means? In my opinion, it's quite obvious: PiS is trying to take control of the Tribunal by any means necessary, even by breaking the law. The party's leader, Jarosław Kaczyński, doesn't respect the notion of modern democracy, with all the checks and balances that limit the government's power. He wants to have the absolute power over the country, so he keeps putting his representatives into every institution he can. First, he designated Duda to be the president, then he designated Beata Szydło to be the prime minister - with both of them just being Kaczyński's pawns. Now he wants to put his pawns into the Tribunal, so that the Tribunal wouldn't oppose any of his decisions.
Kaczyński actually made his intentions regarding the Tribunal clear today, during a pro-government manifestation. During his speech, Kaczyński said the Tribunal sold out to foreign interests (as well as to the interests of shady Polish groups that don't have the society's good in mind), a "rampart of everything bad that has been happening in the country for the last 26 years". He openly said that he needs to take control of the Tribunal, because, otherwise, it will stop his party from implementing all these amazing new projects he has planned.
He has also said other interesting things today, as well as during a big TV interview he gave on Friday. For example, a few days ago, there was a talk of possible debate over Poland's current situation over at the EU parliament - and Kaczyński said that the Polish EPMs who were in favour of this debate are basically traitors to the nation, "Poles of the worst sort". Today, he said that people who organized yesterday's protests are Communists and thieves. As for all those thousands of people who attended them? Well, they are "weak in the heads". His exact words...