1) On the Sidious fearing Vader, youd have to give me time to pull up that one, a friend on Discord showed me the quote once, Id have to ask him wherenthat was when hea online
2) Mace and Dooku being comparable to eachother is stated many times, you could easily hunt this down. If anything, Dooku was SUPERIOR to Windu, as "The New Essential Guide to characters" states that only Dooku and Yoda ever bested Windu, "Labrynth of Evil" states he was the orders most agile instructor and swordmaster. "Yoda: Dark Rendesvous" states that aside from Yoda (who is > Windu and Dooku, who are as we agree, a tier below him), only Windu wouldve been his equal on neutral ground (which is true since this was two and a half years into the war, where Anakin was more or less an 8 to Dookus 9, so to speak, going to a 9 near the time of ROTS). Its also implied that Dooku was, similar to Windu, a master of all lightsaber forms or at least multiple forms, as he taught Grievous, who used Jarkai, Qui Gon Jinn who was taught in Ataru, Soresu (he had to since he taught Obi Wan Kenobi, whonused it against Maul) and its implied he integreated Djem So into form since he relied on strength (which would explain how Anakin learned it despite Kenoni not having any accolades for it, Kenibi knew it but didnt use it). and again, he instructed the jedi and was one of the best teachers (all jedi learn Shii Cho). He also likely knew a lot of Niman since he was highly skilled in integrated force based attacks into his lightsaber sequences, a core principle of niman.
In summary, he had to be at least moderately competent in Shii Cho (known by all jedi), Makashi (his preferred form) Soresu (taught Qui Gon eho taught Kenobi, who knew Soresu enough to contend with a master of Juyo in Maul), Ataru (taught Qui Gon), Ataru (taught Qui Gon), Djem So (also taught Qui Gon who relied heavily on strength, even if Dooku himself didnt. Qui Gons Padawan taught the premier Djem So user of the Era in Anakin), Niman (this is conjecture to a degree on my part, admittedly, but it does fit into his use of the force being integrated into his dueling, meaning he at least grasps its principle, even if he isnt jack-of-all-trades as a fighter), and Jar Kai (taught Grievous and Ventress). This leaves only Juyo/Vaapad.
3) Vader died way too slowly for it to be anyrhing else. He wasnt fried, his cybernetics were. If not he wouldve died on the spot rather than taking a few minutes.