Easy Way To Avoid Tackles
One way to dodge an opponents tackle is to simply do the spin move with the O button. A fast player like your RB will make a very fast spin move and make your player go to the direction you spun about 3 yards leaving your opponent with broken ankles. The spin will not work with some one who is slow such as your QB (unless he is fast) because his spin isn't as fast as the RB's. If your RB is an impact player, your running game should get at least 200+ yards a game.
How To Be Really Good In Dynasty Mode
Go to rosters at the main menu. Choose the team you want and make all of their stats 99. Then start a new dynasty and all of your players will be awesome.