I think nails are out of the questions for glass.
As far as glues for the Lexan, you might want to test your glue on a small area first to see what effect it has on it.
I think glass shelves would be pretty costly if you were to run it around the whole room, but not knowing what your budget is for this display, you would probably do well to use a non hardening glue to hold the track down. That way, small expansions from temperature changes won't break the bond.
Either way you go, all your minor flaws and wiring will be visible so you will have to do a top rate job on installing it so it looks good.