Reminder, Balud should still be less than 16 while all this shit is going down, this is taking into account travel times, the cholera recovery period, the time it actually takes to do diplomatic stuff with all that shit he had to deal with, and the installation of the pumps along with teaching people how to use and maintain them. If he was 13 when the Prince showed up at the academy, and according to the king he dealt with the situation abroad far more quickly than most diplomats could, that's still a time period of a year or two, so he should be either 14 or 15 now.
Diplomatic missions takes years, especially if one of the countries is exchanging new technologies or arranging marriage alliances (which take between months or years alone even between nobles of the same kingdom) or settling previous goofs by the higher ups of one of the countries at the table.
Still though, why do some Isekai authors believe that their MCs need to handle everything asap before they turn 18? Spacing everything apart makes things much more believable and gives the author leeway to properly write up their MC building up their relationships and personal capabilities.