ok im gonna grammaticallus proper for this, sharing some of my own stuff too
High school: High school is temporary, but the years are no joke. Adults know it's just a small part of life, but it's still a few years. You can endure it if it's bad, it can leave some marks on you. Biggest problem with a bad high school experience is that, depending on the degree of the problems there, it can intervene with your development, delaying it until later. Social skills, emotional management and such. Most people here note high school sucks, and that's a Big Truth I guess, but the universal experience of high school being awful has a large degree of variation. Most here are nerds and have experienced the bad side of it probably, but there's a lot of stuff me and people in my life have personally been through that left quite the mark on me, to an extend more serious than what most people are talking about. Severe depression, massive delay of my developing social skills, near wrong radicalization, dropout NEET stuff. OTOH it has given me some resources to help people out that end up in holes similar to mine (because as with the other Big Truth, I don't think universally avoiding cases like mine is systematically possible, so at least people like me are useful). So feel free to ask, always.
For your particular case, I don't know about any sort of Jesuit environment where you live, so I have no clue as to the nature of it. Just the fact that it's religious doesn't mean the experience is necessarily as awful as mine (even if there's some red flags there). People can often see past political differences at any age, it will more have to do with what they think of you as a personality. But if it's just regular social suckage due to unaligned interests and lack of chemistry... There's a quote from some show, I think it was god damn Modern Family, where an adult talks to a teen. Something like "When I was your age, everyone tried to fit in, to be the same. Then suddenly, almost overnight, everyone wanted to be different." And it's pretty useful advice. High school is a semiforced social environment with a multitude of interests and professions stacked on top of each other. As you grow older, carve out your hobbies and professionally specialize (or not, lol), you'll naturally align with other weirdos that you'll fit better with. Adult life is different than high school. I like the advice of a lot of people here, that you should find clubs aligned with your interests and so on. It's pretty darn good advice. Find something you want to do the most and do it. Usually that'll help you carve out some friends.
Love crap: Yea, there's not much to do about that depression. It gets easier as you get older, but mostly because you'll have previous experiences giving you the resources to handle it better. (Also, as you get older you'll usually be more comfortable about yourself being alone; I managed to find this comfort at age 30 myself.) Mind you, if the depression's "just" because of a crush you didn't get with, it's normal and part of a healthy life. I'd focus on stuff that you find interesting or fun, even if you find things are pointless. My common note on depression: Life has no meaning, watch cat videos. Anything that gives you happiness has value to you, therefore it has value. Respect your dopamine. Who cares about meaninglessness if you're comfortable, eating some good snacks, and playing D&D with your buds. I try to make this distinction a lot - there's meaning and purpose and stuff, which is abstract, but you live in the concrete, experienced world. Whatever abstract pointlessness the universe has doesn't actually have anything to do with your concrete lived life.
Love takes time to get over, and it just sucks, and there's not much to do about it. Even with my comfort with my singleness, I'm currently just after the tailend of a 2 year emotional dip after a particularly brutal breakup. It's gonna suck
But hopefully your situation isn't gonna last as long; from what I can tell from your posts, you were just dismissed, she didn't actually hurt you the way you can be hurt. (My latest ex stole a lot of money from me, among other things.)
Sexuality and gender: I have less explicit advice about this since I knew about my admittedly strange situation here from a pretty early age, and was comfortable with it from like 17 and older after I realized boys are fun to kiss too. My gender identity is so fluid I don't really find a huge discomfort in presenting as male as I do. Other posters here have much better experiences (some having much more pronounced struggles than me) and you should listen to them over me here.