I'll tell ya what buddy. There are two sides to anxiety. 1) The side where it's almost impossible to muster up the strength to stand against it, and 2) the side where you realize that once you stand up against it, you realize the anxiety itself is constructed by your mind, and that the issues, when handled right, were not as bad as your mind made them out to be.
I'll try to address all that you said in the OP.
Regarding your dad, it's clear that he's grieving the fact that you and he are not on good terms. At least from what I saw in the OP, it makes it seem like he loves you and that you both treated each other like stuff. Since you stood up to him first, your dad probably sees you as uncompromising. If you can find it in your heart to apologize for what you've said, you should invite him out to some place, buy him dinner, and talk about it. This will not only help repair your relationship, but show him that you want his fatherly love to reach you.
As far as your girlfriend goes. GTFO. Don't deal with that bitch. Let her deal with her problems. If you feel any pity, then tell her that it's sad to watch her sink into such a demanding and unsatisfying lifestyle. (Or however you see it. This is just my perspective.) If you stay with her, she'll take her problems with you. It's clear that her shameful lifestyle has already done you in, so just get out and don't deal with it. If they come over to harass you again, loving tell them off and threaten to call the police. If they're harassing you, they need to GTFO.
I disagree completely. As a strong extrovert, being alone is just as bad as being slowly stabbed with needles.
That said, I can deal with being single. I just can't live without other people.
I also agree with you, and I'm a strong introvert. Really the only thing that will make people happy* is to be selfless and forgiving and be with selfless and forgiving people. Though I need alone time, I cannot be happy without interacting with someone.
*Using a more "inner satisfaction" kind of deal. Like the kind of feeling where you see the most beautiful sunrise in your life and you feel amazing inside.
As for the food poisoning, just use caution, man. Don't leave things out, refrigerate or heat them outside of the bounds of 40°F to 135°F. If you went out to a place that gave you food poisoning, just don't go there. Or if you're allergic to something or think you may be, avoid eating that.