This is a really interesting, albeit quite politically charged topic. I will start by addressing each of the claims.

The Revolutionary Tribunal was not a show-trial. The outcome of trials was not predetermined and only around 60% of those accused were found guilty.

The actual statistic is 64% of the people tried were executed. 32% were acquitted. The rest received prison sentences, or similar punishments. So this affirmation is fairly accurate. These numbers are however averaged out. In reality, the executions were not evenly spread throughout the years of the revolution. In Messidor (June/July) of 1794, at the height of the Terror, 1005 trials were conducted, and of those, 79% were guillotine sentences. This is why the Terror was seen as an acceleration of violence, and the trials were believed to be getting less and less lenient as time went by. Generally, the condemned were 20% aristocrats and clergy, so they were overrepresented compared to the national distribution.
(See: Liste des victimes du Tribunal révolutionnaire à Paris, 1911.; Gresle François. Tulard Jean, Fayard Jean-François, Fierro Alfred, Histoire et dictionnaire de la Révolution française.. In: Revue française de sociologie, 1989, 30-3-4).

Georges Danton actually was guilty of co-operation with the British government, based on some British primary sources.

One important piece of evidence in the Danton trial was a letter from the banker Perregeaux, in which it was alleged that Danton, alongside others, had received a bribe, with the intent of “pushing the jacobins to the paroxysm of fury”. The idea the Danton “deserved” the sentence, as is implied by Žižek here, is outside of the scope of history, but there is some evidence that the bribe did in fact exist.
(See: A. Mathiez, Le banquier Perregaux, Annales révolutionnaires 1919, pp. 242-243. See also Danton et l’Or Anglais by the same author).

The royal family was actively plotting with the enemies of France to overthrow the revolutionary French government.

This one is not very controversial. If nothing else, the "fuite de Varennes" of 1791, during which the King attempted to escape Paris to join Royal sympathisers, was made for the explicit purpose of restoring the monarchy.
(see: André Castelot, Le rendez-vous de Varennes, 1971, librairie académique Perrin.)

After the Thermidorian reaction, the resulting white terror was just as bloody as the revolutionary terror, and the victims were far more likely to be from amongst "ordinary, low people."

The "White terror" of 1795, killed around 2000 people (only slightly less than the 2585 who underwent guillotine executions). The most significant massacres took place in the prisons of Lyon and Marseille. The violence was targeted against former revolutionaries, but in a rather loose way. Some people were killed by association too, if they had been friends or relatives of one of the accused. Those killings were characterised by a high level of violence, and a form of ritualisation. The bodies would be often mutilated, thrown from high structures, or in rivers. The perpetrators of the violence were not prosecuted with much force, which some scholars argue, encouraged further violence.
As for the “ordinariness” of the killed, according to Clay in his paper on the subject “Victims and executioners belonged generally to the same socio-economic backgrounds.” The majority of both were in the class of artisans.
(see: Stephen Clay, « Justice, vengeance et passé révolutionnaire : les crimes de la Terreur blanche », Annales historiques de la Révolution française, 350 | 2007, 109-133.
Jean-Clément Martin, La Terreur, part maudite de la Révolution, Gallimard. Et: Contre-Révolution, Révolution et Nation en France. 1789-1799, éditions du Seuil, 1998.)

Robespierre and Saint-Just were not dictators. They were aware of the threat of personal dictatorship (of the emergence of a popular strongman, like ultimately happened with Napoleon) and consciously refused to go down that path. They were committed to republicanism and instead of simply eliminating all opposition through terror, they thought that they could defend their government with passionate speeches in the National Convention - a naivety which actually contributed to their downfall.

This one is quite difficult to answer succinctly, because it is more political than empirical in nature, so I will only give a few indications. When Žižek states that Robespierre believed he could defend a government with nothing but speeches, and that he was a “moderate”, that's an exaggeration. Within the political categories of the time, he was not a moderate, he was unambiguously Montagnard, which was a radical faction. If speeches were enough, there would have been no need for a Tribunal to “punish the enemies of the people”. Žižek’s argument makes an appeal to Robespierre's psychology (with the anecdote of him walking and rehearsing his speech, "thinking" about how to improve it), which is a difficult claim to prove. The same can be said for the claim that he and Saint Just predicted Napoleon’s rise to power. Whether they accurately guessed that the next regime was going to be worse than them or not, this says very little regarding the factual conduct of Robespierre as a leader.
To summarise, there is a part of the literature that states that Robespierre acted in ways similar to a dictatorship (See: Soboul Albert. Problèmes de la dictature révolutionnaire (1789-1796) . In: Annales historiques de la Révolution française, n°251, 1983. pp. 1-13.) Other parts of the literature argue that this is a conservative or anachronistic view. (See: Boulant Antoine, Le tribunal révolutionnaire. Punir les ennemis du peuple. Perrin, « Hors collection », 2018, 300 pages.).

Overall, whether Žižek’s empirical claims are true or not (and a number of them are), the question remains of whether these facts are representative of the history of the French Revolution, and whether they support the wider point Žižek tries to make, regarding whether or not the Terror has been judged too harshly. To this, I will simply say, as a French scholar and as an eighteenth-century historian, that the history of the Revolution is a very delicate, controversial, and nationally important subject. This means that literature on the subject is often written in a conversation with present issues, and not simply as a way to better understand the past. The subject is also very heavily studied, from almost all possible angles. Lefebvre said as early as 1932 “Two books on Danton. Is he fashionable again? A few years ago, [the historiography] was more oriented towards Robespierre”. (See: Boisson Jean-François. Danton : Réflexions sur une histoire interminable. In: Raison présente, n°74, 2e trimestre 1985. École - Société. pp. 93-111.)
This means that rehabilitating, and then condemning, and then re-re-habilitating the Revolution, the Terror, Robespierre or the Vendéens, according to political agendas, is a staple of this literature. In fact, most books that touch on the Revolution or some of its central figures start by a prologue either stating “everyone says the Terror is bad, but in fact….” Or “these days everyone says that the Terror was good somehow? But in fact…”. To finish in the words of Christian Legault: “If we have stopped to approach these men for political reasons - either to respond to other institutional discourses or to keep the historical discipline “protected from ideological debate” - on the other hand, voluntarily setting them aside also arises from political motivation.”
(See: Michel Biard et Hervé Leuwers (dir.), Danton. Le mythe et l’Histoire, Paris, Armand Colin, 2016, 240 p. Review by Christian Legault.)