I have a similar issue with my own daughter as well in that often she is my most difficult child. We were going through a rough phase recently (taking toys, hitting, pushing,yelling, having tantrums) and what REALLY helped was positive reinforcement. I know it sounds simple, but I realized I wasn't giving her enough "positives" in a day. And I don't mean just saying" good job" when they do something good but to really play it up and be like " wow did you just share that toy with dcg? Wow I am so proud of you! Good job! Dcg is soooo lucky to have a great friend like you! You're a GREAT sharer" I found saying things like :
- you're a great sharer!
-you're a great cleaner upper!
- you're a great walker! (when walking using the rope on the stroller)
-you're a great helper!

All helped to change her perception of herself into a more positive one and it drastically improved her behavior. Consequences for bad behavior are necessary and obviously should have their place but we forget about consequences for GOOD behavior, we let it go unnoticed. Give it a try! Good luck and hang in there, it's hard being mommy and caregiver at the same time.