Elbow strikes is more powerful than punching! I like how you use your whole body for your elbow strike! Rotating your torsio does give you more speed and striking power.
Alot of people will tell you that clenching your fist reduces the power of the strike. Something to do with tensing some of the forearm muscles reduces the strength available to the arms and shoulders. No idea if it is true or not, we would need to do some sort of measurements of striking force.
It's possible, especially if you get hit around the eyebrow area. There's not much tissue between the skin and bone to cushion the strike so the skin can split easily. It's happened to me while sparring. I train hard so I've learned the hard way to use headgear with face protection. Remember, you fight like you train, so train like you wanna fight.