[psy_wombats]

Alright...

Motor Speed: You can't get a motor to go faster than it can mechanically move. So if you're assigning the PWM 255 or 0, there is no way to get it increase its speed... Unless you redo your gearing and select a different gear ratio.

Autonomous: Can't help you much here. You'll want to be more specific on what sensors you are using. What exactly will your limit switch be? To drive for a certain number of feet, you need at least a geartooth sensor hooked up. Then just measure the amounts. There are plenty of GTS threads floating about. Search for specific issues.

And in the future, please don't use caps locks... It makes your post very hard to read, and decreases my chance of reading it. Thanks.