No you dont have permission to access and use those assetts as you see fit. Read the TOS. You dont actually own ANY of the software you have purchased. Blizzard or otherwise. Its BS, but its the case.

No, they didn’t. Private servers are like piracy and emulation. It would be more accurate to call them pirate servers.

Uhhh... I hate to break it to you... but the very game and assets itself are inherently copyritten material. You couldn’t take a direct copy of Stormwind, plop it down in your game, call the game something else, and expect not to lose a lawsuit for copyright infringement.

They didn’t completely recode the game, they built their own server code yes, but not the game itself. The name and art assets are all blizzard owned.