If Dooku never told...

If Dooku would never have explained to Obi-Wan about the Republic being under the control of Darth Sidious, and hence Palpatine, would the Jedi have ever come to that conclusion on their own?

It was a bold move by Dooku, to test Obi-Wan's reaction. He knew he was trained under a radical Jedi - Qui-Gon - who was also Dooku's padawan. To see if OB1 had any radical streak in him, see if he could be willing to join his side, and maybe be a Sith convert? The details of how Dooku changed to the dark side are still unknown.

Was Dooku necessarily evil though, or just misunderstood?

starwars Like all people working for palpatine/ sidious they were all puppets for his master plan in taking over everything and getting revenge for the sith on the jedi and ever anakin joined the ranks of the order he was like " I think i'll get rid of dooku now thatI'm going to get anakin to the dark side" which he managed to do from anakin killing dooku.

Dooku wanted Obi Wan to become a sith and destory Sidious. Much like how Vader tried to turn Luke in ESB

I doubt the Jedi would have found till it's too late. They spent like 2 deacades without knowing of Palpatine's influence in the Senate, I doubt being mixed up through 3-4 years of war is gonna make their path any clearer, especially when said influence is the Good Guy's leader.

starwars he wasn't trying to tempt obi wan over to the dark side because he knew that he was to engrained in the jedi beliefs he was just a stepping stone to anakin. Do you think sidious knew like yoda did what anakin did to the tusken raiders before he told him as palpatine?

I think you are incorrect. Dooku, like Darth Vader in ESB, wanted to run the show and to do that you needed to kill Sidious. It is in the movie, Dooku asks Obi Wan to join him to defeat the Sith Lord. It is fact that the Sith all want turn on each other

Makes sense, thats what I thought too.

Dooku had many different annex points as to how he would try to take over the Sith.

dooku had no intention of being the main sith or turning obi wan to the dark side, he was just trying to make himself look like he trying to fight the sith to try to fool obi wan. he only told them about sidious because he couldn't help himself in revealing that there was a main sith lord and he wanted to show off his powers in the end of ep2, to kinda show there was another main sith much more powerful. The jedi search all the politics to see if anyone is found but no one is even found supicious so the jedi think he's lyeing. they intercept a message that no doubt tells them that sidious is real but they still dont think he's controlling the senate. This is all in the book the Labyrinth of Evil to prove it