For a general understanding of pad placement principles, go to the Globus site, click on Guidelines, and consult the additional videos clicking on Pad Placement Videos
Further to your list above, rise time only serves to make the contraction more acceptable, and in that sense it helps you increase intensity. Make it longer, and it would add fatigue without results. Make it shorter, and the sudden jolt may keep you form increasing intensity. Number of reps, on/off times, depend very much on the type of training, and the goal. Charlie’s protocols are the best around for sprint training.
I see from your guidelines a notable absence frequency, and pulsewidth duration. Unless you’re using an old-school machine offering only Russian stim, which is fixed at 50 Hz 200 microseconds, with the modern generation of e-stim machines, you also have these two parameters to set. Frequency basically determines what type of fibers you are targeting; pulsewidth has to do with the muscle group, because larger muscles work best with larger pulsewidths.
There are machines that regulate based on voltage (constant voltage machines), and machines that regulate on current (constant current). The best machine in the market (Compex, Globus) are constant current. That means that once you crank up the current to the desired value, the machine has a microprocessor that continuously monitors the conductivity of your muscle and increases or decreases the voltage to keep the current constant. As the session progresses and your muscles warm up with more blood, the conductivity increases, and you will find you tolerate the session better and comfort will increase.