Question About Front Derailleur and Cable Jacket

Hello!

I am trying to keep my Concorde as OEM as possible. One of the items on my "Put It Back" list is the front derailleur. It came with a Simplex Prestige. I believe it was model AV 223.

Many years ago, the Delrin self destructed. I was working "7-16's" at the time, so I took my bike to a local shop. They were able to fit a Shimano. It never could do all gear combinations, but at leat I could ride. It's still on the bicycle. Soon, I hope to find an affordable Prestige to install. (I recently found one, but it turned out to be 28mm. The seller thought it was 28.6.)

My question is about the cable jacket. I do not remember if there ever was a jacket on the front derailleur cable. By studying the metric 28mm  Prestige, it looks like the actuating arm 'boss' should have the cable jacket pushed into it. I also think, but am not sure, that the chain guide is moved by the movement of the jacket, not the wire inside.  ( I also think the hub on the actuating arm on the 28.0 is on the oposite side from the 1-1/8" arm. The 28 faces the front of the bike.)

But, the questions that stump me are:

Where does the cable jacket originate? Under the plastic guides or somewhere near the shift levers? What secures it at the non-derailleur end?

My rear derailleur has a short length of jacket from a bracket on the chain stay to a hub on the derailleur body.  The Shimano front replacement has a short piece of  plain tubing only where it passes under the bottom bracket. I put that on after the bike shop installed the derailleur to protect the paint.

Do you all know what diameter the jacket is and does it need end ferrules?

Am I right to think it shoudl be the kind with the strands parallel to the cable? (Not spiral wound)

To me, it seems like the bare jacket goes into the bottom of the boss on the derailleur's arm & pushes against the top of the arm's boss. The boss on the derailleur's shift arm does not have a place for a set screw. I think it passes through the boss & goes into an opening on the body of the derailleur and is held by a set screw. 

Please pardon me if the answer is obvious. For some reason, I can't seem to grasp the concept of how it operates. I get lost with the jacket pushing the arm, but being stopped by a bracket.

My Excuse- I'm amazingly dyslexic & quite often left -is-right, up-is-down & vise versa. Physics goes out the window. Must be one of those days today! (Hour and a half plus 6 or 8 Previews to write this- Yep, it's one of those days. Keeps life entertaining!)

I've attached some photos. Two are views of the cable guide on the down tube and one is the shifter lever cable exit. The 4th is the wrong derailleur I bought to show the cable boss. Please pardon the paint chips. Someday, i'll find a matching paint color.

Thanks Very Much for sharing your expertise!

Paul