Can we not blame the MC too much? He's not exactly believing the FIL, he's being threatened by the thought of his child being subjected to the experiments instead. He's basically being forced to choose between Doyoon and his child. He's trying to reach his mate for days and he has never briefed on anything so, he can't have the full picture to think of what to do. It's not like he has money or power to resist either. ML left him to fend for himself. Whether MC did tell about the dad's threats in full or not, Doyoon should've anticipated the worst given how long he knew his father. And seriously, even if MC did not believe the father, what is he going to do then? Wait? And if the FIL himself could not care less if his own son becomes a lab rat, there's no saying that he would actually execute his threats. He said it himself. He's ready to do great lengths for success. In this case, MC could not do anything. That's why he's worried about Doyoon. If he do this to save their son, Doyoon will resume as his father's lab rat. But since he's not even there or any of his men to monitor what's happening, MC was only left with one choice and that is to take the surgery and take his child out of there. It's not just money that's hindering MC, anyway. It's also the grave side effects post-surgery. So he's also literally staking his own life here. He only has his child left. So, for G**'s sake, cut him some slack. And do not bother to blame his past decisions because we are all in here now. That's his only way out and choice.