Responses
This is a good theory but he had the power for a few days after becoming a vamp, and killed the guys who bullied him before they planned on leaving the next day. So he had control of his powers, sadly. My guess is that when the dad overwhelmed him in strength he decided to use his empathy to win, otherwise if he didn't have control over his powers even when the dad ripped his heart out, he wouldn't have ate it no matter what.
That's possible as well. Let's see how things unfold
I think Yohan killing Hayan's parents is misunderstood in a way. It's for sure that he killed her parents. And that he's a total crazy now. But do you remember the first flashbacks, when Hayan's father first went to stop Yohan and embraced him to console him. And Yohan was himself very confused with his own powers as it was new to him. Hayan's father understood. But when he got hypnotised by Yohan, it might have been an accident. Yohan might have newly acquired it and lost control of it. Coz actually it was Hayan's father who took his own heart out because of hypnosis. But Yohan later lied to Hayan about how he betrayed and took her father's heart out. And when Hayan's mother found Yohan, before Yohan could explain anything Hayan's mother preassumed the situations and set both of them on explosion. So I think Yohan accounts himself to be guilty.
And hold himself accountable for killing those two dear to him and doing injustice to Hayan. But might have later hone crazy trying to shift the blame to someone else. Idk ... But I think there's more to the past than what it seems ...