the vertical line is the easy part. the line connects the label (A20) to a point. it is easy to just drag the label close to the point. my husband just poked his head in to remind me of an appointment so I have to go. when I opened your file, I could not see the back piece at all. look in the draw mode at the lower right corner and you will see the names of the two groups. there is an icon of an open eye or closed eye. I opened the "new groupback" and the back piece became visible
It seems that you created detail for only the groupfront. you see this by going to details mode - you have only one detail and it appears to be the front.
I would recommend that you close they eye on front and open the eye on back and create detail (using seam allowance tool in draw mode) for groupback. then go to mode details (at top of screen) and you should have both details. in the details mode you can drag one so they are not on top of each other. this will not affect the positioning you see in draw mode.
I will check back later in the day. I hope this helps