Here's the latest version, with modifications as recently discussed:
I'll also post some partial plans, zoomed in. I've started to add in dimensions to locate curve centers and radii, and guidelines to lay out the angles. Obviously, this can become a very cluttered drawing if I tried to fit in dimensions for everything, and it seems like you've been able to continue laying track without having such dimensions previously, so just let me know if you need more information than this. For curves with the center in the aisle, to lay them out you can just tack up a temporary board across the aisle, locate the center, and scribe the curve with whatever trammel you prefer. On my own layout, I just clamped a board in place until the curve was drawn.
The climbing grade in Naijahville was pushed further to the right; this required a handful of changes around the Union Station. I've added in the scenic element of a Main Street; I envision this rising and falling, fluctuating between the high line and low line, tying them together in a way. This street provides bridges over a few key areas to hide things I think should be hidden, such as the backdrop penetration.
You should notice that I tweaked the backdrop a bit, too; I straightened the left end, as you requested, and the right end I bent just a tiny bit sharper, to make room for the passing siding on the high line. The Main Street passes right in front of the backdrop where it's labeled "Downtown"; this gives the opportunity to use building flats or even a decent photo mural backdrop of storefronts on the far side of the street, with full 3D buildings on the near side of the street. At the location marked "+1.0", Main Street can either rise up and cross at grade, with crossbucks and all, or else it could drop down about a half inch to pass under a bridge here. If you're familiar with Madison Road in Oakley, where is drops under the old B&O tracks, that's a case where a level grade crossing was turned into an underpass later on, that's kind of what i was thinking. This is often done on busy mainlines. But if you intend to do so here, be aware that it means cutting out some of the plywood to allow the road to drop (i.e. you must cookie-cutter the road).
Wherever there are bridges along the rising grades, I suggest you just lay the WS foam risers right on through and then cut and remove the risers where the bridge will drop in. From your pictures, I think that's already what you're planning on doing.
I added in the indication of a plywood mill, to load up your centerbeams, but as with other industries I'm not getting into the nitty-gritty of trackwork here. That can all be played around with once you figure out the buildings that will occupy the site, and you could just scoot switches around until you find something you like. I have Main Street starting out high on the left, so that there can be a service road leading to the Grain Mill branching off it, and also so that it forms a bridge to mask the tunnel entry (in fact, with care, the bridge could be made *as* the tunnel entry, a sort of optical illusion). As the road goes to the right, it drops down to zero elevation, and doesn't rise again until you get past the "+1.0" marker; it would need to rise to about two inches in order to bridge over the tracks, so this makes downtown a bit more interesting.
As always, glad to hear any comments.