I am certainly no expert but I think the problem might reside in your “Glas” material transmission line.
Transmission is actually “fake caustics”(or at least it is in MATSpider), and having both fake caustics and real caustics in the same material tends to cancel out any noticeable effect.
Try deleting the “transmission” line entirely and changing the “radiosity” parameter from 0 to 1. This worked for me on several occasions. Also, if you are using any kind of GI or ambient lighting, like Eeshlo’s WORLD LIGHT option, it will make caustics difficult to pick up on a surface unless the intensity is very low.
You already seem to have a better grasp of the program than I do, and I have been pestering people for a while, so don’t give up on it. By the way, that is a nice picture — I bet it took a bit of time to render.
You also might try out Mrmunkily’s tut – http://www.jonlake.com/proj/LightflowTut/ look at his glass parameters closely.