Spoiler
He is not. He is just, crazily in love with Jaehan to the point where he can't get Jaehan out of his head even during the whole time he was in jail due to drug scandal case. Even at the lowest point of his life he worries about Jaehan more than himself. I will say... Heegyeom is 'crazy', he is crazy just like Jaehan, you will know what I mean later. That is it . I can't give more spoilers than this cuz I'm afraid that if there are too many spoilers, the story won't be interesting anymore.
Spoiler!
I can't really say that there is not. The problem between them is more of a misunderstanding that causes anxiety, insecurity, and jealousy due to lack of communication and honesty with each other. If I had to be specific, there would be an actor from Heegyeom's former agency when he was an actor, which isn't really a threat but Jaehan sees him as a threat. And about Jaehan's marriage, Jaehan actually has no intention of remarrying but Heegyeom feels anxiety because of it.
Uuh...this much.... I feel like I spoiled the whole story ʘ‿ʘ
can someone please spoil me, is he actually gonna take revenge?