Your JS doesn't work either (the testing i==6 one). If you follow the logic by hand, you see that you hit the i=loopindex condition twice. i starts at 3, then when loopindex = 3 you multiply i*2, so i=6. But the loop is still going, so when loopindex=6 the condition is met again, so i*2=12. At the end of the loop i=12.
For the Wait, add the action Destroy:Particles in the On Start to get rid of the original.