OP, I really like your question. Indeed the author didn’t write a one-dimensional villain so you will have to wait to get his point of view from his own words. Both Ines and Carcel also have their points of view on his behavior. In the meantime, the crown prince has indeed been holding back and restraining himself like he told Ines in this chapter when he said he’s been patient until now. I guess that’s his attempt at being ‘reasonable’ to prevent driving Ines to suicide again. In the future we will learn how much he has been holding back, how much he knows, why he’s dead set on Ines, why he disregards Carcel, why he’s delusional, etc.

Both FL and ML know their oast life and working hard not to repeat it again. The Crown Prince knows the most. He knows each life he died tragically. How come he doesn't want to be a good person and change his ending? It's like he doesn't care about his life at all. All he can think about is Carcel and Ines