Hi A.,
Every mom who is being honest has had a moment where they would love nothing more than a holiday. Unfortuately, it's never really mom's day off, so you have my heart felt sympathy. LOL
Lots of times when kids are agressive it has a lot to do with how they feel about whether or not they are communicating. If they can't express themselves (not your fault but because they get so frustrated they "lose" their words), if they feel they aren't being heard, if they don't have the appropriate words, or don't even know WHY they feel how they feel, they can act out aggressively.
A lot of practice helps. Telling him what to say, what to do and acting them out in play situations is like any other kind of practice. The more you do it the better you get at it and eventually it comes naturally. Helping him identify feelings, starting with the simple ones and getting to more complex ones, and how he feels physically when he feels those emotions as well as what triggers them, will help him start to control them.
Instead of trying everything, try one thing in the way of consequences and stick to it. And find one that you can apply anywhere and will matter to him. For instance, if you hit, you are done. No matter where we are we will go home, no matter what you are doing we will stop. Keep it really simple and really consistent. If he gets further angry, stick to your guns and try not to elevate with him. Stay calm, and if you need to remove him from the rest of the group. His fit shouldn't be his punishment for you disciplining him.
Take him to get tested for allergies. A little bit of discomfort could lead to a whole boatload of rest for both of you.
Hope this helps,
L.