That's why I don't think that the Zoey thing is a ticking time bomb anymore, she's not the same character who'll blow up over the slightest thing, she might be angry at Zoey, but the MC hasn't done anything wrong, he's been completely honest with her about how he feels and his intentions, and he misread the situation.
Personally, if my girlfriend told me that her ex tried to get back with her, she rejected him, left a party that she planned to spend time with me, then told me she loved me for the first time, why the fuck would i be mad at her