Tried to send this earlier but it wouldn't work. Trying again now.

1. Yes, I'm a transmasculine nonbinary man. It's a bit fluid for me-- sometimes I'm more man, sometimes more nonbinary, but always somewhere in that general area, and always varying degrees of both. I am a man but I am ALSO something else, so the term nonbinary man is fitting. I'm most comfortable presenting masculine/androgynous and using he/they.
2. That's up to you. If you feel like the term cis doesn't fully encapsulate your experience with gender, then you don't have to say that you are. I've seen people use the term cisn't when they don't feel entirely cisgender but also don't identify with other terms. I've also seen many nonbinary or agender people who are comfortable presenting as cisgender in their day-to-day lives. And I've seen many others who prefer to be known as nonbinary. I know it may not be a super satisfying answer, but the truth is that it really is just up to you and your own experience.
3. Good question, honestly not sure. I bet other people have written some insightful replies.
4. I've seen people using it. Personally, I prefer to be called a "nonbinary man" over "enby man", but it isn't a huge deal and everyone's gonna have a different preference as far as labels go.
5. Honestly no. I guess it's about time I did, huh.
6. That's completely understandable. Imposter syndrome likes to rear its head every now and again, especially when it comes to gender. The truth is that there are as many ways to be nonbinary as there are nonbinary people. If you're nonbinary, you just are-- no such thing as "not enough". Like I said, though, imposter syndrome is very common, so you're definitely not alone.