speed and length

[epixoip]

The rate is likely falling because the GPU is throttling itself. The 295X has a very low Powertune target temperature -- it has a hard-coded maximum value of only 75C (compared to the 290X, which has a max target temp of 95C). In your screenshot, both of your GPUs are practically already at 70C, so you're extremely close to the maximum temperature that card can handle. This is why we have never recommended the 295X for hash cracking.

For your second question, read the wiki article on rules and check out the -j flag.