school me on dist

I know it may be kinda tough to read my highlighted areas, first area says ..............big cams give poor cylinder filling at idle...........

Is that because the RPMs are low, the valves are open longer and higher so less vacuum = less air fuel ratio ?

Second says .............Poor fill and or low compression means we have to light the fire in the cylinder earlier with more advance at idle.............

Why is this, I dont understand

Third over on the right and top says..........Remove the oil pad in the center of the pad.............The only dist I had with an oil pad was the old points type dist.

Was this a money saving tactic at the rebuild shop with the new ones. Do I need it?

4 Highlighted area says........The stock unit comes with a light spring and a heavy spring with a hoop on one end. This is good for pick-up or heavy vehicles that cant tolerate alot of timing cause of constant heavy load.........

I dont understand this, I am only reading it but have no clear understanding of what I am reading!!

Last lower right says..........These springs are so light the advance is coming in at idle...........

Id like to better understand why this is not a good thing?

It is my understanding at this point that the vacuum pod is only pretty much being worked off idle to sorta help get vehicle rolling and also at cruising speeds but not heavy acceleration cause at that point there is a loss of vacuum and so the weights within the dist are dictating the amount of advance but I dont understand why once the RPMs are up and the weights are spinning why we even need the pod.

Hope all this makes sense. I am going to re-read this article another 6 times and I am sure I will pick up a bit more.