The QB run on an option is actually extremely easy as long as they aren't bringing the house. It doesn't matter how fast your QB is (I've successfully run the option with a 68 speed QB). You just have to learn to make the correct read. If the read man (the one with the orange R over his head) comes in for the blitz run it with your QB, if he stays on the outside hand it off to the HB (same goes for the shovel and pitch plays). As long as you learn to read the blocks you can get 7 yards a run easy. My advice would be to run the option trainer in the Nike Trainer. It's how I got good at making the reads.
Scrambling out of a designed pass on the other hand is a much more difficult. For this you DO need a fast QB. The only times I will run are if there are 3 rushers and everyone else is in coverage (I'll run it up the middle), or if a play breaks down and I find that one side of the field is open I'll scramble to that side and run it once I get to the outside.
Hard cuts (using the left stick to quickly change direction) through blocks and trucking are the biggest keys to success when running with the QB.