I don't see Inseo doing it this way
I actually do understand why he's acting like that now, I've seen ppl holding back on smth and then letting all out and not being to keep it within boundaries
I'm not saying it's good or healthy, but he was obviously obsessed with Yi-Heyok for very very long time, he just kept it contained. And he could probably do it because Yi-Heyok was rather easily manipulated by him and never got involved romantically or sexually with anyone. Before Inseo was also convinced they never will be together in that way, now suddenly he's confronted with possibility of Yi-Heyok breaking up with him and them not even being able to be friends after that. I think he's acting that crazy cause it's almost like his worldview or the way he imagined his life and their relationship was going to go changed completely.
The only thing that stayed the same is that Yi-Heyok must be in his life, so he grabs on that extra hard, while everything else seems so uncertain and unsure.
However, I still don't see Inseo doing THAT
Unless we're going for proper manic episode that is
Like Yi-Heyok probably can tore the chain from wtvr it is attached to and no way he'll let this slide
Inseo is smart and strategic enough to not do smth like that
But oh well, we shall see...