First off -- good for you for asking these questions at this stage in your life! You are way ahead of the curve.
Are you sitting down? I'm going to give it to you straight regarding the PhD route: Don't do it. The economics of teaching are not good right now. Academics is a different world now than it was 20 years ago, and PhD degrees are not what they once were. It is a dangerous blind alley in the world of careers, and it will probably hurt your chances of FIRE.
My spouse is a university professor, and has run search committees recently for open positions. For each entry level tenure-track position, they receive ~150 applications. As you can guess with supply/demand numbers like that, the pay is low. Tenure track teachers work their asses off, and I don't know many who can manage a good work-life balance. To make matters worse, most colleges and universities are moving toward using more part time and adjunct teachers to save money on staffing. These folks (all with PhDs) earn far less than the tenure-track people. Most of the teachers I know (tenured, tenure-track, and adjunct) say they made a mistake and wish they could undo it. They went into it feeling like it was a noble calling, and found something completely different. They do NOT feel that the joy of teaching young people makes up for the bad work conditions and low pay. In fact, they say that for every great student they get (there are some) they have to cope with 20 poorly prepared students who have no idea how to learn and don't want to do any work.
When students ask DH if they should go on to grad school, get their PhD and teach, he always tells them to run away. Run far away and get a job in industry somewhere. Not all professors tell their students this. Some professors still have the mindset of 20 years ago, when the teaching situation was different. They aren't necessarily aware of today's realities.
Sorry to come on all doom and gloom. I could go on, but you get the picture -- the economic realities of getting a PhD and teaching are bad right now. Strongly recommend that you stay the course with your current major, get a job, and get on the path to FIRE. There are many, many ways for you to find your passions in life and be fulfilled. There are many ways to teach/connect with others without going down the PhD path.
Feel free to PM me if you'd like to talk to my DH. He can give you more details from "the trenches" if you have questions. :)