Regarding point 2:
You can read about this problem in this old closed mega thread here.
Maybe you find also some hints for point 1 there if you scroll a bit up and down from the point which i linked.
It is a bit messy, because different topics there are discussed at the same time.
Having said that reminds me, i like to advise you to start a new thread if you have a new question. Because if someone searches for the solution of the problem we are talking about now he would have better chances to find them in a thread with a title that fits.
What we are discussing now has nothing to do with:
Capture the random value used to extrude each island to be used as a scale factor?