You are correct - on the map you referenced, starting on the left at the gas station (shameless plug for Freddie's, gas, food and air) the route travels in an arc back around to M76, crosses the highway, and dead ends about 400 yards into the woods. the VV Mapping maps do a better job than the DNR maps - VV Mapping shows the biggest vehicle allowed where they overlap, whereas on the DNR maps the solid lines (ATV trail) cover up the dashed lines (ORV Routes).
For the St Helen maps, stay tuned - the proposed "bucket" of ORV routes in the area has been tentatively approved, connecting a lot of the little bits and pieces of route in the area. Not such a big deal for 4x4 users, but should make a whole lot more opportunities open up for non-SOS licensed SxS users. We are still working out the details, but we should get Pinball Alley back too.