I agree with Jaekyung rebuffing Dan, but not in the manner in which he did it. He was so cruel and brutal about it (which represents much of their relationship really).
By taking on side jobs and feeling tired all the time, I feel that Dan probably compromised his work as a physical therapist. Which is partly why Jaekyung feels so frustrated – he's paying top dollar for Dan to give this gig his very best. And it was all over a trinket (albeit an expensive one) that Jaekyung could easily buy himself.
Yes, it's the thought that count and Dan bought the present out of the sweetness of his heart, but I feel that Jaekyung always made his intentions and expectations of their working relationship clear from the get-go and is paying Dan the requested salary.
Anyway, from a romantic relationship viewpoint, Dan is much too good for Jaekyung.
Kim Dan confessed while being under the influence of drugs, even though he didn't remember the next day. I think Joo Jaekyung is going to do the same in the next chapter. These idiots. Toxic relationship or not, the romantic feelings are mutual
Heesung was introduced to be a foil to Jaekyung. They are exact opposites.
Heesung seems like perfect boyfriend material – says the right things, buys the right gifts, showers Dan with sweet attention, but he's fickle, superficial, exploitative. If he won Dan over, he would happily ditch him with the next breath without another thought. His "love" seems unconditional (on the surface) but it's completely self-serving.
Jaekyung seems like a total asshole and seems to say and do all the wrong things – but he's the asshole who rescued Dan from loan sharks, paid his debt, gave him a place to live with no end date, visited his grandmother, paid her medical bills, doesn't seem like he'd ever turn Dan out onto the streets or ditch him any time soon, even if his jinx was resolved. Maybe their arrangement is exploitative and Jaekyung is forceful. But every time Dan expresses gratitude, Jaekyung pretends his kindness is 100% self-serving and I don't think that's totally the case. I think Jaekyung is now protective of Dan in his own way.
In a previous chapter, Heesung's minder said that he's fickle and falls in and out of love and love bombs people, which is what he's doing to Dan. I think it's the thrill of the chase for him and he's able to abruptly move on from Dan. Potato sees right through him.
I'm not saying Dan's relationship with Jaekyung is healthy either. But I can't see Heesung taking the initiative to visit Dan's grandma (without turning it into a photo op anyway), rescuing Dan from the loan sharks, paying his debt and his grandmother's hospital bills. Jaekung says that having Dan live with him is not to help Dan but for selfish reasons, but regardless of his motives, he has a constancy about him that Heesung clearly lacks.