I am a Sev fan too, and from what i have heard, he was rumored to have been fighting with the 501st when the Imperials invaded Kashyyyk. Dunno where i heard it, or if it's true.
i think A. its on a poster i have, from the star wars comic.
I think that most of the clone wars rocks, Like the bits with durge, that's good. The bit with Greivous and his elite on coruscant is well done too, I always wondered what happened there. But yes, the rest can be a bit slow. Oh yeah, the bits with ARC troopers rocked too.
I think Jango is good, not as good as Boba (obviously), but thats like saying a Dodge Viper isn't quite as good as a Ferrari. He is still one of the best, and is certainly worthy enough to be a Fett. But he is in a strange place in the storyline. He is the Republic army's template, yet he works for the Separatists. But he has a more 'complete' set of Mandalorian Armor, as boba doesnt have the shin armor or the thigh armor, but Jango does. Jango also has a different view on Starfighter Combat. Boba opts for the more stealthy approach, yet Jango goes for the destructive version. They are just 2 great Bounty Hunters, but the son learns from his father, and from his own experiences, so he is going to be better.
It's gotta be Durge, because Durge v.s Obi-Wan (clone wars) was quite close, and Obi-Wan could kill Montross easily.
You have missed out Aurra Sing and Jodo Kast, those i can remember off the top of my head.
I prefer IG-88 though.