I dont know that I have any answers for you other than that I also have asked the same question myself and many other questions beside. I believe what you feel is perfectly normal. I'm 43 now and have been asking and trying to understand why I am who I am for a long time now. I understand and have empathy with your feelings on how others act but at the same time you crave a level of approval and love/acceptance from these people.
To be honest your questions hit the nail on the head! The problem with life is that it doesnt come with a user manual and we are left to work it out for ourselves.
I believe to understand others we need to understand ourselves and why we do things.
In life there are 2 emotive forces. That of PAIN and PLEASURE. My desires in life are maximum pleasure and complete avoidance of pain. These are the basic principles I base my decisions on. Everyone has a need to avoid pain! These forces have directed my life for the larger part without me realising it. For a long time I have avoided doing many things in my life through fear of failure, PAIN.
Its difficult to understand what other people do or why they do it. Do other people make decisions because they are the wrong decisions to make or do they evaluate their options and make the best choice that they can. In fact I would go as far to say that there is no such thing as a wrong decision. The decision you make may not turn out the way you want it but at the time you made it, it was the best option for you
If you make a decision that I completely disagree with is the problem that you are completley wrong!! Or is the problem that you have not made the decision that I would expect you to make or behaved in a manner that I would expect you to behave?
There are basic needs that we have that drive us, that change our focus in life and are the basis for everything we do.
The first need is for Certainty. This a primary need and not something you have a choice in. Every human requires this. Its not a desire. Its something you have no choice in. This is a need for comfort and stability and the avoidance of pain.There are many ways that we achieve this level of comfort.
A few that come straight to mind are things we know will give us instant certainty and comfort. Food, chocolate, Alcohol
What about Predictive certainty - All people will dissapoint!
We can do things that give immediate certainty but that dont improve us.
More positive methods that give certainty is Faith,Family
Whilst needing certainty it would soon get pretty boring if you where sure of everything all the time so yes we also require levels of Uncertainty in our lifes.
Again this is a need and not just a desire. We need to be challenged to have variety and diversity in our lifes.
See a new film, have a conversation, do something you have never done, develop a new skill.
The need for Certainty and Uncertainty are not in conflict but serve to compliment each other.
All humans need Significance, people need to be needed, need to feel important, need a sense of purpose, need to feel loved in some way or to have a unique sense of meaning.
THIS IS A NEED and not a desire or something you have a choice in.
The biggest driving force in a humans life is Emotional need.
People achieve this need in ways that are both constructive and destructive but nonetheless the same need is being serviced.
Putting other people down to show you are better than them
Some children in recent years have went on killing sprees in response to needing significance.
Having a negative Identity can make you significant.
Many woman feel the need to be needed and achieve this when they have a child.
To a man he may feel significance through promotion
Belonging to a faith or religous group
Have a partner that adores you
Having friends that appreciate you.
Whatever human being sdo they have a reason!
Humans have the need for Connection and Love. This goal in life is probably at the forefront of most peoples minds.
People need friends, familly,lovers!
This need also applies to Religion, Nature, pets, all the good stuff you love to do but also in connecting with yourself.
Lastley we all must have a purpose in life. We need to continually grow, we need fullfillment and need to contribute through doing the right thing for the greater good.
I hope my observations have helped in some way. Take from it what you want and live life with passion