Regarding Ji-ho, Nadia explained her reasoning to him as to why he isnt to be wed to her, and he himself found no fault with which to reply. So unless he has previous timeline memories like her, he has no history with her whatsoever. Nadia is a catch, sure, but shouldn't be notably remarkable to him. And yet here he is, pining for her, someone he's not said more than ten sentences to. Is it really so galling to him that one woman found any reason to not marry him?
My impression, is that he was an incel before he came here, and now, Dragonslayer or not, an incel he remains. He's focused entirely on the one woman he was once promised, but now cannot have. He's in an unhealthy state of mind, and likely won't be receptive to another prospective wife.
He is, to conclude, a fool.