Take it from someone else that spent a long time self-debating over whether or not they were “really trans.” The fact that you’re agonizing over this means you’re almost certainly trans. Like, 99.999999% certainty here. And if it turns out that you’re actually the remaining 0.000001% then that’s fine too. What’s important that you took the time to study and challenge the very concept of yourself. That’s wonderful. If it wasn’t for the pandemic I would strongly urge you to visit one of those spaces you mentioned. Anyone that would attend such a place just wants everyone else there to be happy and safe to let everyone understand themselves. You would be welcomed, I have no doubt about that.
As for how I became comfortable with myself it was more or less just immersing myself in things made by trans people. Books, comics, games, even if it was just scrolling through some random trans person’s Twitter feed I could see myself reflected. Practically none of it reflected me perfectly and there was plenty of stuff I bounced off of but the fact that so much of it could get as close as they could was incredibly validating. I did eventually go see a therapist that specializes in gender issues that really cemented my conviction to being not cis but immersing myself in trans culture set up a non-trivial amount of foundation. I would later be invited to a Slack group run by a small group of friends who are mostly LGBTQ+ people, and a local group for autistic trans people that mets once a month up until the quarantining. We’re working on coming up with something to do remotely.
If you need someone to listen to you (be it questions, ranting, or whatever) then I would be more than happy to listen. Be it through text or audio, public or private, or even inside a game, I am willing to be there for you if you want it. We can shoot fascists and capitalists in Warframe while venting about male puberty. We can gush about our favorite TV shows while visiting in Animal Crossing. We could send forum PMs about pointless bullshit. I, and so many others, just want to help you be you.