Was Dooku more interested in his political agenda, or the Sith cause? How loyal to Sidious was he? How muchdid he realize how evil his intentions were? It was unclear in the films for me, not enough was shown of his motives and character.
He was a true Sith Lord with the mind of a politician, much like Palpatine was. He was loyal to Sidious and the Sith right up to the moment he realized he was disposable. I have no doubts he knew that his actions were evil, but keep in mind he had become disillusioned with the Jedi Order and with the Republic, and likely saw a Sith Empire as more pragmatic than a corrupt Republic. Likely a viewpoint that he used to his advantage when recruiting Separatists.
"I have become more powerful than any Jedi" - Dooku "The Dark-side I sense in you" - Yoda. Dooku was interested in power and didn't care how he obtained that power...even inciting war and was looking forward to ruling at Palpatine's side. "I have good news my Lord, the war has begun" he was definitely a Sith.
"Count Dooku is a political idealist, not a murderer." - Ki-Adi-Mundi Ki-Adi-Mundi seemed to believe in him at one point. I think Dooku became disillusioned with the Jedi Order and the republic. I think his turn is similar to Anakin's turn. By that, I mean I don't think he set down the road for evil purposes, I think he had a goal, and somewhere along the way became obsessed with the power and greed overtook him. I'm unsure if Dooku knew of Palpatine's plans. It is entirely possible that Dooku thought the clone army would simply betray the Jedi and turn the galaxy over to Dooku (or Palpatine) to be ruled. Otherwise I don't think he would have put so much effort into winning the war on the confederacy's side. So if he didn't know of Palpatine's plans, I think he really may have believed in the CIS. I say this to support his reason for joining Sidious. Sidious offered him the power and position to make his ideal government a possibility. And of course along this path of his righteous turn to the dark side, his priorities shifted, and power became his goal. If anybody got hurt along the way, he no longer cared. His loyalty to Sidious is a totally different question, but I think he was wise enough not to challenge his master.
I agree with most of what you said here, his initial motivations were largely along the lines of abandoning a corrupt Republic, and he loses sight of this along the way. Perhaps like a more politically-motivated Vader. But for the most part Dooku did know Palpatine's evil intent when he organises the Separatist movement. By the time of AOTC Dooku was never intending to follow this through to any kind of reality where the Separatists won the war. He, like Sidious, was planning to betray them and start over as a leader of A Sith Empire. It appears in reality Dooku held some disdain for the non-human members of the galaxy. For example, his comment to Poggle during the first CW battle "It doesn't seem possible. How could the Jedi amass an army so quickly?" is totally feigning ignorance as he was involved in the creation of the Clone Army in it's early stages. He also takes their Deathstar plans with no intent of them being including in it's ultimate purpose. In the ROTS novel he apparently believes that if Anakin turns he and and Vader will lead a Sith army enforcing the rule of Palpatine's Empire, but he is of course not included in the actual final plan. His orders in his final duel was to try and kill Kenobi, and drive Anakin into a state of rage at his two master's (Obi-wan and Palpatine) dilemma, then Palpatine would stop the fight if Anakin proved superior and they would take Dooku prisoner. Dooku would then "repent" when the Empire was formed, and with the help of Palpatine's corrupt Senate and courts would be released and join his Master in ruling the Empire.
I definitely got the impression Dooku had good intentions and tried to rebel against a corrupt and manipulated system in the only way he saw possible, but perhaps got more deeply influenced and manipulated by Sidious as time went on, sort of distorting his view and actions, but he perhaps still thought he was doing the right thing in the long run, and for the greater good of the galaxy. I think Sidious may not have divulged all the information of his plans after taking over the senate/republic. We never actually hear or see Dooku actually doing anything evil in the films, infact what he does say seems like goodness and righteousness (telling Obi-Wan about the Sith Lord controlling the republic, and asking Kenobi to join him to destroy the Sith etc...)
We know from Gunray "I'm not signing that treaty until I have her (Padme's) head on my desk" that Gunray wanted Padme dead, and had asked Dooku to arrange it. Suggesting that Jango was hired by Dooku to arrange Padme's murder.
Haha I misread that title and I was like "Ah crap, I shouldn't have taught them how to get past the auto swear filter" Fun fact. KotOR has some drunks who say the word Sith, and the subtitles put it as "Shith". So if you ctrl+f naughty words in the script, you'll find that. You can imagine my surprise when I saw those four letters were in the script before remembering those lines
I don't think he's particularly interested in the Sith cause for the Sith's sake. It's his own cause that matters, and if they line up, that's cool. He was very loyal to Sidious, and didn't see Sidious' betrayal coming. He was loyal because their goals are aligned, they supposedly want the same thing. So, though it's terribly naive, why wouldn't Dooku be loyal to Sidious? They're on the same side, with the same goal. I guess Dooku never quite learned his Sith lessons. I'm not sure how evil he thinks he is during the prequels. I'm sure at one point before the films he thought he was doing the right thing, doing good, and he may still be telling himself that he is doing the right thing by the time of the prequels. If you're looking for a percentage, I'd say he was probably around 90% Sith at that point. I think there was still a chance for him to be redeemed. Well, that's the real trick, isn't it? And it's gonna cost you something extra. Ten thousand. All in advance. What I mean is, Dooku is lying and deceiving, and his actions are hidden from most (but not us, not really). He is part of the plot to assassinate Padme, he is part of the plot to create an army of abominable clones, he leads the plot to attack the Republic with a massive army of droids in what he knows to be a war entirely cooked up by Palpatine and himself, and he puts Obi-Wan, Anakin and Padme into the arena to fight to the death for the Geonosians amusement. These plots are all pretty clear in the films, and so is the immorality, though Dooku cloaks it all in feigned innocence.
He believes in the Sith power and thought he could use the power as a tool to achieve his own goal, but didn't truly see the way of the Sith, treachery, lust and manipulation. Other than that, yeah he's evil.
Sith are as varied as the cosmos. But they are all Sith and subscribe to the fundamental beliefs of that Order.
I think he was completely Sith in that he would never return to the Jedi. On the other hand, he didn't seem to be completely evil, at least not like Vader and Sidious were. I do think that he thought we was doing the right thing. I don't know how loyal he was to Sidious; he seemed to have a mind of his own, in a way. As far as whether he was interested in a political or Sith cause, I don't know. Like you said, not much at all was shown in the movies.