Although I can appreciate your emotions, the flight changes are bound to happen, whether it is with Delta or another carrier. The airlines are looking to make the best use of their planes and if your flight was underbooked, it made sense to cancel it and rebook you on another flight.
Would you rather they just cancelled your flight and didn't rebook you?
Regarding your crushed luggage, although I'm sure the airline representative was not as emphathetic as you would have liked, you have to understand that although it was ultimately a problem with the service you had with Delta, it was not directly her fault. She is under a lot of pressure right now and I think giving some of the airline personnel some slack is probably a good idea because a lot of them don't even know if they have a job tomorrow. Do I think she could have handled it better, absolutely, but I can also look past some of the attitude. Remember its better to kill them with kindness then it is to argue your point.
Again, I'm not trying to discount your emotions, but some of it is just the nature of the beast that the airlines are right now. Be happy that you made it there and back safely, you were able to spend time in one of the most magical places in the world.
Consider that if this was the biggest problem you faced, that in the end you're more fortunate then 99% of the people in this world.
I've learned to deal with change, it happens. You do the best to avoid it, but even with the best made plans, things sometimes mess up. I want the most for the money I spend, just like the next person, but sometimes, even the best spent money doesn't go as far as it should.