A lot of your worries are similarily shared by almost every trans person at some point at least, usually at several points. You are definitely not alone with what you are feeling. Everyone has their own spin on it, but nearly everyone has had it. Not uncommonly it's soon after beginning transitioning medically.

This might not be an issue for you, but another thing to think about is whether you have some transphobia against yourself in some way, or internalized transphobia. Many people can struggle with this and it can make answering those questions more difficult. Again, might not be an issue for you, but throwing it out there since a lot of people can struggle with it.

As far as being non-binary, one person I know who comes to mind transitioned from female, had top surgery and is on T but is non-binary and prefers they/them pronouns. They have a beard that I'm jealous of and overall seems like a pretty cool person. I'm sure they have their downs, but they seem to be doing pretty well. Now, this person prefers to go by neutral pronouns, but there's no rule about what pronouns you should have. They do get misgendered as male a fair bit, but it sounds like they've found a way to deal with it on a personal level. Really, that shouldn't be something they have to do, but unfortunately it's the way things are right now.

Anyways, what I'm getting at is if you feel more comfortable on T there is no reason to go off of it, regardless of what your gender is. They are two seperate things.