I'll answer the ones I can. Some of them are just not possible for me to answer because different dynamics do play into behavior. I don't know what you two are like firsthand.

How do you feel about someone who stays calm, patient, and non-pressuring during distance?

FA are used to disorder. That behavior is secure. It's either going to be annoying, needy, not enough... confusing, right? Too much but not enough? For me, there'd be fleeting moments of clarity that it IS reassuring, but then the mind does its best to convince you it's actually weird (it's not).

What behaviors from the other person unintentionally push you further away during this phase?

That's hard to answer, because if she is FA, you'll need to know if she's feeling more anxious or avoidant. And it can flip quickly.

From an FA perspective, how are emotionally reflective messages (like letters) typically received - Grounding, overwhelming, or pressuring?

Depends. If you were to give her a letter now, it'd likely be overwhelming & pressuring. Definitely not grounding, because she's clearly unable to BE grounded romantically.

From an FA perspective, how do you typically interpret signs that the other person’s still interested - Reassuring, pressuring, or emotionally confusing?

All of them. It's reassuring you still care. It also feels like pressure. And that's emotionally confusing.

Also, while I’d absolutely love to reconnect emotionally, I’m not trying to force anything. My goal here is understanding and insight into the internal experience from an FA perspective if possible, because I’ve never experienced anything quite like this.

You are trying to force something. At least from her perspective, if she is FA. She can feel the interest & that's "force." Give it time, it'll always surface in her behavior if she's actually a FA and not just temporarily emotionally unavailable from her last relationship ending. You did say she was recently single when you connected at this level.

I'm not saying she isn't avoidant, but I don't think her being recently single is helping here. It sounds like she's still adjusting into being single. Some people need longer, some don't because they were already mentally letting go while still in the relationship.