Wow GKelly that's a fascinating OP. In some ways I've felt what you feel, in other ways not at all. I'm going to hang around and see how your topic develops, see if I can gain more understanding and maybe contribute.
I moved away from my home town (LaLa land) to a small city (Santa Fe) and I too felt isolated. I had a nice friend I met on C-D who helped me, but in the end I developed only a few friends, neighbors, nice people but the friendship didn't stick after I realized I wanted to live in a big city and came home.
Another experience, perhaps an opposite of yours, I was always afraid of being alone. I wanted to go camping but nobody wanted to go with me. I finally planned a trip through AZ, NM and UT, figuring I'd always be within two days drive of getting home if I went through friend withdrawal. As it turned out I had a great time! I met fellow campers at each stop! I ended up spending almost 3 weeks on the road, and found all the friends I wanted along the way. Admittedly not permanent friends, but fun to be with people you will probably never meet again. Ultimately I bought a 4x4 and ended up tripping out to the rim of the Grand Canyon several dozen places, months of total time spread over several years, camping alone for 2-3 days at a time never seeing another human being, and in later years I got a dog who liked it as much as me. -- And this is the lesson I learned: I don't need other people to make myself happy. I like other people but they are not a requirement. Happiness comes from within, not from without.
Somehow I feel that my comments do not address your problems. Probably we are opposites, or at least different in a significant way. I was afraid of being alone. I tasted it. I discovered that it simply wasn't an issue. I'm happy with people, I'm happy alone. Okay I'm happier with a dog.
With or without people. People are simply not a corner stone of my happiness or my fulfillment in life. Highly desirable but not essential.
I'm glad you are in therapy. You have a good resource if you have the right one.
And trust people? My favorite saying: "In God we trust. All others pay cash." Hell no I don't trust people. I like to give people the benefit of doubt, but they prove themselves before I trust them. You gain trust only by long time relationships. It's foolish to trust people you barely know. Not trusting people is not a problem, it's your survival instinct.
The only problem it can become is if you have a pathological distrust of all people that you cannot overcome. You trust your cousin. You trust your therapist. That's a start.
You're young, away from home, at school. That's hard on anybody. You'll graduate, you'll settle somewhere. Maybe you'll move somewhere else. That's the time in your life you can focus on friends.
I had a small clique in college, most of them from my same high school. But I attended college locally, chances are you will have to make new friends. Seek people with common interests. I was interested in computers, my college had a computer club. Get involved in some activities related to your school.
Trust me on this, based admittedly on a short sample of you as you presented in your OP, but I feel that you do not have any major problems, other than problems you share with many people your age, problems that will solve themselves as your life progresses.