I would be very nervous to book 2 tickets with a connection time of just 2h30m, usually I aim for 4h+. But if they actually let you re-book for just 200€ that would be very reasonable. Have you made sure with the phone agent that this isn't just the change fee and you won't get a fare recalculation on top of that?
As for misconnection insurance, they usually require a longer transit time but if yours works with 2h30m, its not a bad option I guess.