Baitcasting beginner - hopefully not the same ol' questions

My kids are getting into fishing, and I've been wanting to learn how to
use a baitcaster. I researched on the web, and have tried to educate
myself on using this reel more effectively. This is a fairly cheap
Shakespeare Agilty reel if that makes any difference.

I've become pretty proficient setting the spool tension knob, I also
figured out by reading that you should cast with the reel facing you.
I've been getting pretty good results casting when tying just a bobber
or a lead weight to the end of the line.

Here are my questions:
1) The magnetic "cast" control affects the spool's spin rate at the
beginning and middle of a cast, is that correct? Why is the spool
turning faster than the tackle as it is being reeled out? I guess I
don't understand the dynamics here. How will different settings heavy
vs. medium affect my cast?
2) What has the bigger influence on backlash? Spool tension or magnetic
cast control? I guess I don't understand how they interact.
3) Does everyone "thumb the spool" when they cast, or do they just let
it run until the tackle is about to hit the water?
4) What difference in technique allows an experienced user to use less
magentic cast control than a beginner? What is the beginner doing
differently that would be problematic?
5) I've had a lot of trouble casting very lightweight stuff. I read
that this is normal, but I'm still wondering why.

The biggest problems have been trying to cast a rig with - say a treble
hook and dough bait, with a bobber about 2ft up from that. I set the
spool tension knob correctly, but get the "mother of all birdsnests"
every time I cast. Makes no difference what the magnetic cast control
is set at. Grrrrr.

Now strangely enough, I experimented moving the bobber down closer to
the hook, and the backlash problem goes away.

Now obviously I must be committing a cardinal sin by trying to catfish
with a baitcast reel or something. The only thing I can figure is that
having two (nearly) equal weights at the end of a line separated by
some distance greater than X causes the whole system appearing much
lighter than the combined weight to the baitcast reel. But wait - if
that's the case, my spool tension knob is set too high and should
LESSEN backlash. Anyone have the same experience or can shed some light
on this? I'm really baffled...

One other question about technique: Does everyone get satisfactory
distance out of just "flicking the wrist" or do most people tend to
also use the elbow in conjunction with the wrist flick? Will using the
elbow exacerbate backlash?

Thanks for the help.