After playing a number of times, our whole play group didn't understand why the turn order for using your prestige went clockwise from the player with the most. Sure it makes it simpler, but also makes it very unfair to the player with the 2nd most prestige especially if they are sitting to the right of the the player with the most.
Well, I disagree that it's "unfair" to the player with the 2nd most prestige...they know the rules and the result is hardly a surprise. To me the question is whether your variant results in a better game. I've actually tried it this way a few times and I prefer the original rules. You don't have to spend all of your prestige...if someone beats you this year, save some prestige so that you lock up 1st place for next year.
Was also thinking of allowing a player to keep using their prestige until they tie or go below another player, at which point that player would be the active player to use their prestige. Visually it would then be easy to see whose turn it is to use their prestige. This might be way too powerful though, so would have to think about it.
Been there, done that. This makes the festivals take much longer, adding a lot of time to the game and doesn't yield enough benefit imo to be worth it. While I think your first variant is ok but just not to my preference, I wouldn't try this one again.
Our group also seemed to think that 1 prestige for start player was too powerful.
Now this is one I personally wouldn't touch. I assume that the costs have been balanced through far more playtesting than I've been able to do.