I have no friends. How do I fix myself?

I have no friends and that bothers me to the point of depression (in the colloquial sense). I am considered "difficult" to deal with and my few, past friends were almost as "difficult". The loss of my last such friend was the tipping point at which I decided to look for help. So here I am, stuck, looking for advice, literature and maybe online support groups. I want to understand what is going on with me, where I am on the mental map and what my options are before I dump all my money on psychotherapy (with no social network my savings is my only security).

My background: I am cis male, mid 40s, the oldest child, mixed ethnic background, long-term single and currently work in strategy for a large IT company. My parents kept relocating throughout my early childhood which, I read, are the formative years of social skills. As a child I withdrew to books and other solitary activities. In school I was bullied a lot and found "Ender's Game"-style violence to be an answer. Relations with my parents are complicated; we can't find ways to express our love. I don't talk to my syblings. I find small talk excruciating and have low tolerance for anything I can't find purpose in. I enjoy tet-a-tetes but hate groups. My place is a mess which I do not mind. I work out a lot and am health-conscious. I have no patience for details. I am a serial job hopper because after a few months I end up having poisoned both my social and professional context beyond repair. Finding employment used to be easy because I mastered the interview game. I enjoy the thrill of interviewing, the validation of receiving an offer, handing in my resignation, moving to a new place and starting a new life. But lately I am becoming sloppy in interviews, making mistakes, being too sure of myself and consequently not getting offers. The realisation creeps up my spine that I am losing the one game I was good at, which was my escape from reality and that I might be stuck here forever.