How can I discover my life mission and dream job?
My advice to you is to not be in a rush to find your life's purpose - let it grow and become clear as you engage in the adventure of living. To see one's life's purpose clearly is a bit like developing a photograph - the blank photo paper is placed into the chemicals in the tray and as you watch a clear image comes increasingly into view. If you wish to progress toward your life's mission keep the primary focus inward on your own personal development, (this is the chemical in the tray), not on the photographic paper (this is the job or career). Both are needed, but it is by getting the chemicals right that the image becomes clear on the photographic paper.
Further Help and Resources
If you wish to learn how to listen to inner guidance and through such attentive inner listening find your path toward your mission in life I strongly recommend my book Unfold Your Wings and Watch Life Take Off.
I feel you need to stretch yourself, beyond the "safe" box of your customary identity, by taking on new responsibilities and interacting more with people that have need of your help. As you discover your own fears and weaknesses, you will have more empathy for those who have the same, and your desire to help will become a more practical matter rather than abstract interests drawn from books. Sooner or later a bell will ring inside, that this is the best way you can be of service, and your life mission will take off.