J.-
The best advice I can offer is this- When your son has a meltdown, try to voice his feelings for him. At this age, he has very strong emotions, but very little vocabulary to name them. When he falls down and starts to cry, it may be pain but it may also be fear. You can ask "did you scare yourself?" or "do you have an owie?". When he's screaming at you for taking away a toy you can tell him that you know that he's dissapointed and angry, but the toy has to go up for now. You can also try re-directing his interest and see if another activity, toy, or something to drink will help him deal with his hurt feelings.
I'm dealing with the same problem in my 1 1/2 year old boy. And as a mom of 3, it isn't always easy to respond promptly to every demand. Be it the kids, the housework or the phone, there's always something.
Best of luck to you. And remember that this time in your son's life will be short. It doesn't feel like it, but you both will get through this stage just fine.
-B.-