Don’t fall into the trap of him not coming: that’s what he wants. Inform him that you wish him to be there for the full time, as he promised you and your parents at the time of booking. If he decides to miss part of it you will be hurt and angry, as you already are. And that he needs to speak directly to explain his decision to your parents.
The time for him to say he didn’t fancy it was before the holiday was booked. He said he would go, your parents booked and kindly paid for it, and he is being rude and selfish towards you all by subsequently reneging on the commitment to miss ANY of it for social things he’d prefer. And for making it so clear that he would prefer the other thinhs to holidaying with you.
He is also proposing to spend family money, which is tight right now, on a boozy weekend (when your budgeting shows his spending on booze is already high) and presumably also increased transport costs.
And then displaying anger when this behaviour is challenged.
This has a bearing on your future decisions on WoH. Sorry that you quit a well paid job due to bad experiences at work. Suggest in considering work options you don’t rule out the higher paid, even FT roles. It’d be taking a big risk, medium to long term, to be financially dependent on someone who behaves like this.
If you continue AH he could, for example, say things like “I work hard / earn the money so I deserve it”, “I missed X [boozy social event] with Y because of you/the DC, I have now planned Z”.