Cretaceous, I do see where you are coming from actually.
Foxy600, I do utterly sympathise with you, perhaps your Mum being diagnosed with Cancer HAS made you a tad oversensitive, again understandable.
Your DD is 4, she doesn't get to call the shots over the entire family's social life. Just because she needs to go to bed at 6pm or whatever doesn't necessarily mean that the whole family has to leave a party in progress and trot home... Unless they want to.
Telling your DD that daddy would be home at 7 and then informing him of such? I have to say, as much as I am the only parent that does anything for my DS (4) if someone were to do this to me, bearing in mind that I've only actually ever been out without DS once (last week) I'd probably throw a bit of a hissy fit myself!
I'm not for a second suggesting that DP's reaction was valid, it wasn't, it was extremely childish and petty. If he had said I'll go back for a couple of hours, and then did come back when the party was finished, then fine. You did however go on the attack and told him to be back by 7pm, or not at all, so of course he took the flouncy babyish option. Many many men in my circle, stepD, DH etc are exactly the same, infuriating!
I'm slightly concerned about how he behaves when he has a drink... indicates a minor drink problem, or one certainly on the way to manifesting.
Don't set yourself or your DD up for disappointment. Tell her that Daddy will be back later, and to tell her to say goodnight at the party. If she kicks off about it, tell her Daddy will put her to bed another day, if indeed he does get to do that.
Like who drives when going to parties, can you take turns? Any chance you can say to DP that next time HE's on bed duty and YOU stay on at the BBQ?