i dont get it what does he mean sunhwa is the one hanging on

Probably the one that still wants to continue the threesome

It means that the twinky is retaining Nanjo from Mok even if unconsciously, mostly because twinky is acting like a damsels in distress in front of Nanjo so he can be spoild by Nanjo's money and gifts...
... ╥﹏╥

so is he basically saying sunhwa is stringing them both along and telling nanjo to give up?

but why would that throw nanjo off?

What Mok means by this is the intention of wanting Nanjo to realise the fake attitude from sunhwa, something Nanjo isn't aware of yet. So, Mok thinks if he tells the truth, like he is doing now, Nanjo might not view Mok as the bad guy... Something along the lines...

Now I’m confused too..

Ah okay thx