It should not be crashing that much. Our alpha testers, and now many here using the beta, are seeing some instability (to be expected at this stage), but nothing that dramatic.
My first question would be about your graphics card drivers and settings. I don't know if the Titan uses the Quadro driver set, normal Geforce set, or a different one. If it uses a Quadro driver, you may need to adjust settings for best performance and stability. Try updating your drivers as well, if you haven't done so already. Terragen uses pretty simple OpenGL functions but for some reason graphics drivers change support of these basic functions between versions sometimes, and it can cause crashes (it still mystifies me why this happens, why some drivers seem very stable with the same version of Terragen, and another driver version can crash a lot).
As for GPU rendering, no that's not possible at this time. But with a powerful CPU you should be fine. The 950 is a bit older at this point, but should still perform decently.
- Oshyan