Considering how Grayson has the tendency to quit his job, dump his exes as soon as he thinks they are not his fated lover and almost try to quit this fire fighter job after sleeping around and cannot find the specific omega, I would say his actions here still make senses. He was obssesed with finding the dominant omega because he believe they are the one, just to find Dane who has nothing matches with his preference except the boob. The date this time almost confirms in his head that they are not the perfect match, it's the final straw that fuels his disappointment.
For Dane, many people has pre assumption about Dane's personality because his past is not unveiled while he is in fact a lot more emotionally distant, reckless to the point of suicidal. It is already hinted through how he distance himself from love and relationship, always prepare to go into danger alone (rescue the dog, do the kidnapping by himself) and is always ready to get up and run away if any trouble comes. He has backup plan for Darling but never himself, and will repeatedly jump first and alone into danger in the future. I have a feeling that him being a fire fighter and cameo in helping other characters in other stories has created a lot of assumption on Dane as the perfect fire fighter with utmost sense of duty while he is in fact more complex than that.
Also considering that both the main characters are working as fire fighter, you will see them continously get into fire, dangerous situation as part of their job. Even if they dont happen to be at the scene like this time, it is their job to go to those places after all.
I feel like there could have been a lot better development of their personalities tho. I've noticed that a lot of background info we have on them actually comes from novel readers who've read way farther than the webtoon has gotten. Maybe this will read differently once it's completed and can be read all at once, but their behavior in this chapter feels so sudden. Like, dane's rejections up to this point havent been enough to discourage greyson (physical fights, willingness to sleep with anyone but greyson, dane not not exactly being greyson's type) but dane's lack of knowledge regarding what a proper date is? Greyson has known from the beginning that dane doesn't share his romantic ideals. I need more convincing than what this chapter gave me. Maybe it's a lot more fleshed out in the novel, im just a webtoon reader so idk.
Also im a bit confused about this backup plan. Has it been mentioned at all here or just in the novel? And dane is worried about darling saying she'd be left all alone if he went to jail cuz the miller's sued him, but would she? Does his backup plan only take effect if he dies?
I understand them going into dangerous situations as firefighters (it'd be odd if they didn't tbh) but the timing of this terrorist attack (as well as the drama of a terrorist attack) felt overly convenient. 1) how did some rando on the street know it was a terrorist attack? Unkess ur in a warzone or are consistently being hit with terrorist attacks, it makes no sense for someone to know in the moment what's happening. 2) ofc it happens right on time to disrupt greyson's doubts about dane. 3) it also provided a convenient segway into dane not caring if he dies. Adding the danger of additional explosives (bc i guess being willing to throw urself into a fire to save ppl isnt enough) feels like a convenient way to retroactively develop dane's suicidal streak (which could have been made more evident from the beginning) and simultaneously evoke sympathy from greyson who was just thinking of leaving him. It's all just too convenient and the webcomic hasn't been consistent in maintaining these aspects of their character.

The characters feel crazy inconsistent this chapter. Grayson being so ready to throw in the towel feels weird. It'd make more sense if he were just angry, but after all the crap he pulled when Dane very obviously hated him and obviously did not believe in fate, and then suddenly wanting to quit just because he doesn't know what a proper date is? I just can't buy that.
Also the reasoning here for dane's willingness to rush into danger and give his life doesn't make sense to me. It would make a lot more sense if he did it because he felt a sense of duty as a fire fighter, doing it because "he has no one who'd miss him" not only completely ignores the cat that his entire life centers around, but also is so obviously just a way for the author to generate sympathy from greyson to "deepen his affections."
A terrorist attack out of nowhere also just feels weirdly convenient. Greyson's character had intrigued me before but this bit felt so lazily written i cant help being disappointed :/