I'll share with you my experience for what that is worth. First, run the mower for a few minutes then stop the mower, turn off the engine and start feeling the pulleys, and belts on the deck. The belt(s) should be warm, not hot. Feel all the pulleys including the idler, the idlers should only a bit warm. The fact that they are wider then the belt is O.K. They just "free turn" against the back of the belt. The hottest pulley will be the one under the engine. Remember, the engine heat is coming down the crankshaft. Be sure to check the blade spindles. Heat anywhere here is your enemy.
Now to remove the engine pulley I use an air impact wrench. An electric impact wrench will do the same thing. Otherwise, you have to access the top of the crankshaft and hold the nut while removing the bottom nut. You may be able to straighten the pulley without removing it. I have done this on occasion. Good luck.