My responses are interspersed with your comments.

The spring that makes the switch pop out is definitely not down in the
distributor!!!  The spring in the distributor simply ensures
electrical contact down in there.  It holds the button on the end of
the wire against a dimpled piece of metal inside the distributor.  

Obviously, there is another spring inside the popout switch.  I have
popout switches here that have been removed from the armored cable,
completely, and they still pop out.

The contact that goes into the distributor makes electrical contact
with one terminal of the condenser (capacitor) and the movable arm of
the breaker points.  When the points close, contact with ground is
made.  When the points open, the path to ground is opened.  

As I write this I have the internals of a Model A distributor laying
in front of me.  

Now, take a look at the side of the popout switch.  There is an
electrical terminal.  The original Model A used a red color-coded wire
running from that terminal to one side of the coil.  

The other terminal of the coil had a black lead that goes to the
junction box on the firewall.  It connects to the "hot" wire coming
from the ammeter.  The other terminal of the ammeter goes to the
negative (hot) terminal of the battery.  (The Model A used a positve
ground.)

Someone offered to send you a Bratton's wiring diagram.  Study it and
you'll see my description is correct.  As I write this I have a Model
A wiring diagram in front me me.

So, stop to think about what I said.  The one side of the coil is
*always* hot.  The other primary terminal of the coil goes to the
popout switch.  When the popout switch is closed, the circuit to the
distributor is completed.  

The points in the distributor open and close as they do their job.  In
effect, when this happens the points are opening and closing a path to
ground. In other words, when the points close, the coil is finally
grounded.  When they open, the ciruit to ground is opened, the field
in the primary collapses, inducing an EMF in the secondary of the
coil.  

I'm not sure what you are saying, here.  If you wire the side terminal
of the popout switch to one side of the coil, and the other side of
the coil to the ammeter, you'll be in business.  

That is, if everything is in order down in the distributor.  Soldered
connections grow old and corrode.  I've found an open between the
conductor in the popout switch's armored cable and the brass button on
the end.  Soldering the button back on fixed things.

Orrin

A Ford of that era cost two years pay for a working man. Anything that valuable is
subject to being stolen. In real costs, cars are cheaper today than back then.

George Patterson
    If you don't tell lies, you never have to remember what you said.

I cannot answer that because I wasn't around in 1928; but, look at it
this way:  The doors had locks.  The ignition had a lock.  Somebody
back then must have thought that security was an issue.

Orrin