Ronaldo would also be wise not to play for another Italian club than Juventus. I think that many fans and enthusiasts like to be seen as an asset there, but it will be different for many supporters. Of course he has the clubs to pick out. Man City was not an option due to the rivalry with Man United. Maybe try another country, Bayern Munich is not a bad alternative and high level too. Or eventually back to Real Madrid? He has won many prizes with Real Madrid and was very important for the team.
What do you mean? Has he really decided to leave United now? I haven't seen the news that he's gone these few days but there are a lot of rumors that don't mean he's going.
Even if he is going to leave, obviously Serie A is not the place anymore, I think, especially for now the Serie A team that is being linked with Roma. There is no reason for Cristiano to go to Serie A and even if it is just a rumor I would prefer him to be at United next season.