Nice revision. I downloaded your file and noticed a few things.
First, the light you set up for back lighting was behind your purple wall, so the light is blocked. It’s ‘Shadow’ setting was turned of as well.
Second, no reflection on the glass. Since we are faking glass, its my opinion (I’m no expert) that an env map reflection helps a lot, because glass and most shiny hard objects reflect thier environment. But the environment should be lit accoding to your needs. I’ve read lighting is the hardest part on 3D rendering and animation. But it is absolutely vital for realism (if that is your intention).
Ok enough of that!
I’ve attched my rework of your glass and the .blend file I updated below.
Take a good look at the settings and changes in the file, and play around with it.
Not perfect by any means, but maybe it can help. Last thing for now, everyone will tell you it takes a lot of tweaking to get what you want on all of you 3D projects, what works (settings) in one place may fail in another.