How do you injure opponents, and can you injure the ref?

I'm getting carded for just sealing out the opponents, so I figured I might as well slide the life out of them, but I can't figure out how to make sure they suffer. My players get injured all the time, but I have yet to see my opponents' players hurt. They pretend to be hurt when they are waiting for the ref to give me a yellow (back when football was a man's game, we used to make fun of players who pretend to be hurt until ref's decision, now it's so blatant and normalized, it's in the game....get it?), but after that, they are fine and dandy running around, and I get sent off for nothing. Any help, I'm trying to hurt somebody here.

Also, why can't we slide on the ref? Maybe shoulder check them when they get in our way? The refs in this game are crooked as a clothes hanger, and my players should be able to voice their frustration by maybe crippling them sometimes. Isn't this game supposed to be realistic?