Here's a start.
http://www.blackhornettechnologies.com/Construct2Stuff/ApaYaa_Stack_&_DropRate.capx
I didn't understand everything you wanted, but the stacking is sorted out.
First, you can use containers to associate objects together. Read the manual for details.
As soon as you start repeating a pattern, stop. Computers live for patterns, so a For loop deals with your stacking.
Your spawning was overly complicated, so that's a bit simpler now.
Edit: on re-reading, this may not be what you wanted, but I'll let you respond.