This is an inner game issue indeed.
I was a bit like you in the beginning of my PU. I couldn't stop reading all this material. I thought, the more knowledge I have, the better I will be. WRONG! Pickup is something practical, like driving a car. You won't learn it from a book. You'll learn it from doing it, experience wise.
So practice like a madman. I'm a martial artist. Imagine how many punches and kicks I had to take before getting good. Not hundreds, but thousands. And I'm still getting them on a regular basis. It's part of being a martial artist. You already feel it coming... failure is part of being a PUA.
In order to get good at pickup you must fail. Yes, you need failure if you want to get better. Because failure is a learning opportunity. What I suggest is to go sarging ASAP and do as many approaches as possible. Your goal is to fail, so you can learn from it, and get better. Next time fail again, learn from it, and get better again.
You will see that if you open yourself up to fail, your ego won't get in the way preventing you from approaching.
And about how not to give a fuck about what others think of you? It's all about your own insecurities. When someone is insecure about himself, that person will try his best to do whatever he can to look better in the eyes of others, thus care what others think about him. The key to not give a fuck, is to truly believe that you're the man.
I was insecure myself before I started PU. Afraid to say what I wanted, afraid to dress in a unique way, afraid to stand out. I was simply boring. I began martial arts and started PU and I soon changed as a person. I don't care anymore what others think of me. Before I started pickup I couldn't think of leaving the house without my hair fixed and all, for example. Now, I don't care. Actually, I never fix my hair anymore now I mention it, LOL! Not even when going out. Chicks love it when a guy doesn't give a fuck about his looks. Be proud on yourself. Oh, and before you start acting like a careless caveman, remember that hygiene is still important though
