
gotta wait until they finished this arc

They might be or they might be not. We're not sure since the update isn't regularly. Some of the readers forgot the recent arc since it's been awhile. For me, I can't read it for now because the pain and wait for more chapters. Gosh. I hate how they suffer . Just I wish that they could go back in their daily life.
I'm not sure if this you're talking about xD I do not understand a little bit of your words.

But you won't expect that someone's been obsessed with the omega uke. What's more that he attempted to rape him after the MC told his mother what happened they immediately move out and stay away from that man.

Oh it’s not that important to the story, the guy was obsessed with MC even before he became an omega.
SPOILER
The sad thing is that after he assaulted (I don’t remember the details after such a long time) MC in the past, nothing was really done to punish him because MC at the time was a beta. Most people didn’t even know he did sth. Now however, the second time that he assaults him (attempted permanent marking, keep in mind MC can not get rid of the permanent mark because of his disorder, so if he really got marked by that trash it would be the end) he gets prosecuted because of the omega protection laws. He gets harsher punishment because ML's lawyer gets involved.
He's planning to kill Carcel to take Ines away since they haven't child together and the rumours about them having a problem made him more bold.
This is just my guess since he's the only one who is obsessed with Ines so much in different way—
Well, I won't rule him out. In stories like these you never know who the culprit could be.
That's fine. He could be the one or he could be not. It's just my guess. Well, we gotta wait for them to reveal who's the mastermind.