Some emitter questions

1. The plan is to have the emitter produce blocks and for these blocks to impact with the player. The problem is if the player impacts one of the emitted blocks, all of the blocks react as if also impacted. How do I change this?

2. I want the emitter to produce a new block when score is at (for example) 20 points. I've been playing around with variables and calculators here but I can't quite figure it out.

3. I want the emitter to produce a block at a new position on the X plane at random. Am I on the right path by using target zones to do this?

Thanks.