Awesome idea! The table is going to be tough enough not to crack, and it's not really likely to flex out at the ends, what you really want to do is make sure that wooden back doesn't bow or pull away from the front at the top of the glass, so you want a strong stable connection from the top of the glass at the front (or distributed across the whole top), to the wooden back.
If I were doing it, I'd be tempted to just build the bottom, top, and back out of marine plywood and router out access holes in the top, then rubberize it on the inside.
Use a paper template and router to trace the profile of the glass in the plywood about 1/4" deep basically so when you silicone it, the glass is supported laterally both directions by a wood/silicone sandwich. Same amount of work and double, double and a half the money and you could do it in acrylic instead.
Another much easier and cheaper idea to secure the top of the glass to the back is to use a nylon or galvanized "pallet strap" around the top (cheap if you can borrow the tool, "universal size" and easy to redo if you eff it up). Uglier though.
Neat project, hope you post the pics!