2 - OK, I think that the best approach for this is having a function to update both: global variable and the text display.
So, using this function you just need a trigger..
- On colision with "sweets: call function Update_Score and don't forget to set the Param(0), Param(0) is the amount of Score that will increase, so, using this function you can have different score for different itens and even when finishing levels.