How can I be the head of my wife and protector of my home when I'm not Bruce Willis?

This is one of those "I would if I could, but I'm just so weak" issues. Being the head of your wife is a matter of obeying God. And being the protector of your home is mostly a matter of not opening the door to the enemy.
The title is provocative and silly for a reason. Media such as movies has brainwashed us to think that in order to achieve anything you need to be the very best - and even then it's a struggle. This makes you lethargic and fatalistic. You don't even want to try. You seek constant validation and become a "mama's boy", thinking that is matter what you do.
The universe is different from the movies (shocker!) and you don't have to have all it takes to solve every problem. The world is different for every one of us. You only need to be faithful in the things that have been given into your care.
Stand tall and do your part. Stop opening the door to the enemy just because you think you can't resist him anyway. It's a trick!
The experience of being a man, trying to provide for his wife and kids, trying to be loving etc. is one that will lead to one of two directions: the arms of God or failure! Point being: you shouldn't try to do this alone. Lean on Jesus.
In order to be the man of her dreams and God's design, you need to become weak towards God and lean on Him to have the strenght to go on.