While I understand your desire to cheat to have a little more fun with the game, I don't believe that story mode is difficult to warrant cheating at all. In my opinion, you're really doing yourself a disservice by wanting to play the game this way. Once the "fun" wears out, you'll likely never play the game again.
Unfortunately, I don't have any advice to help you achieve what you want. Using the cheat engine or any other program to modify memory values might help. If not, then you're stuck trying to create a mod of your own.
It's just not worth it, really.
