Names: You can use the names given at draft time, use names of NFL players past or present or you can change the name of the player to any name you'd like as long as you make it non-offensive to others. You want your brothers, friends, etc., on your team, and see how they would do playing on a real NFL team? Then do it.
Positions: You may play a player at any position if you feel that would benefit your teams chances of winning even if it's not on the players position card. Play your WR at running back, CB at DE, etc,.
Weight: The weights for a position are just a guideline for that player to be at his best to perform at a certain position. Speed is everything in this league.