In general trans people get to define their own etiquette, but when it comes to pre-existing romantic relationships it is at least as much and arguably more a matter for the non-trans partner. In this situation no expectations or judgement either way would be the fairest option.
I don’t know that I’ve ever referred to monetary interests as “pecuniary” interests, either. But that’s still what the word means, because when a person says “pecuniary,” most of the time they’re referring to monetary stuff.
Language is rich and ever-changing, and nobody uses all words with all meanings.
Yeah, it’s hard to change the grammar of your childhood. I’m also a dinosaur who finds that very hard to do. And yet, I have several friends who prefer it. So I try. I’m getting better at it.
I started with written forms – when you write an email, you can stop and think about what words you are using, and actually take back the wrong pronoun before hitting “send”. Or… more to my experience, I can put in the right pronoun, wince a little, remind myself that it’s the right thing to do, and then hit send. I’m getting there. 
That’s actually the default assumption in interacting with anyone. Maybe that person was born apparently male, grew up as an ordinary boy, and still identifies as a man, but lost his bits to an IED in Iraq. Are you going to ask him about it? Are you going to tell him he needs to use the ladies room now, because he no longer has the equipment to use the urinal? No, of course not.
I don’t think that’s entirely accurate- because every definition of “deadname” I’ve seen refers to transgender or binary people only. They don’t simply refer to a former name that is no longer in use simply because someone changed their name. I understand that someone whose name has changed from " Ellen" to “Elliott” is likely to have different feelings about being called by their former name than someone who changed their name from " Bertha" to " Brittany" - but the etiquette is the same, and I’ve never heard anyone call the former name in that situation a “deadname”.
Reference to childhood names is something that comes up frequently, even among cisgender people. I have a friend that I’ve known since we were both in pre-school. At the time, we both went by diminutive forms of our names, and so that’s how we know each other (e.g., “Bobby”, though that’s not either of our actual names). Now, we both mostly go by the single-syllable non-diminutive forms (e.g., “Bob”), but we still usually end up calling each other as the diminutive, because that’s how we know each other.
ISTM part of what get people a bit tied up in knots is uncertainty about what should be the presumed default for reference or address to a person, and that coming from the expectation that there should be a more or less universal presumed default, which grows from centuries of operating under such a system. And IRL, simply informing someone “sorry, this is the right way to do/say it” is not always going to result in seamlessly shifting to the new/right way.
Many people get the sense that now they not only may have to remember a specific form for each different specific individual, but that it may become socially inappropriate to presume a default at all. That change in paradigms can be quite a heavy lift.
And at some point, children ask their parents to stop calling them “Sweetie-bum” or the like.
I could have written every word of this post (except that I have two daughters and a son).
Should it turn out that any of them are trans, that will not lessen my love for my children one iota, or my acceptance of them, or my desire to assist them in life.
But I will say that, for the rest of my life, I will have memories of little girls and a little boy. I can’t see how that could change.
Well, yes, that’s true - I got some extremely rude and prying questions about my late spouse when people found out he was disabled. But we’re discussing the trans and non-binary here, and all too many people both on the internet and out in the real world seem to need a reminder about MYOB.
I use a diminutive of my name, and have since college, more than 30 years ago. My parents know it’s the name I prefer, but both generally still call me by my full name. Well, Mom still does. Dad died last January.
On consideration, I think the reason it bothers me is that using “they are” feels like one is treating the specific singular they as a generic singular they, which is in a way dehumanizing or, at the very least, holding the person at metaphorical arm’s length.
On the other hand, using “they is” makes me feel like a hillbilly.
Just to chime in with my own unimportant take on it, I likewise interpreted your use of the term “devolution” as implying not “language is getting devolved and decayed and degraded, how sads”, but rather “this originally more formal and deferential mode of address has now diffused into the language as a standard second-person pronoun”. Which I think is a reasonable and comprehensible application of the word “devolution”.
So, no movement then? Aw. 
You need at least 50 people a day doing it for it to be a movement, and at least three for an “organization”. Two people, well…
Bravo! Good for him!
It’s the pronoun you would use to refer to a person if you didn’t know who they were.
See what I did there?
How do acting awards with only gender specific categories handle an actor who is non-binary? Page has won many female-specific acting awards in the past and I would expect them to still be a performer who would earn awards in the future. Will Page be nominated in a gender-specific category or will there be a category for non-binary actors?
Right. In a similar manner people who change their last name after a messy divorce - they can get pretty snippy if you call them by their former last name. It’s a different nomenclature (which seems a bit more emphatic?) that I can see may have a bigger impact on some parents.
I have seen suggestions that in the future just having one Best Actor (encompassing all genders) category. However, I don’t know how likely that is. I wonder if the Academy will ask them to choose which category to be considered for (not entirely unlike how movies chose to be considered a Drama or Comedy in the Golden Globes), but that is fraught with peril as well.
Or… if an actor is receiving an award for a gendered “Best” award it could be for the gender they portray…? Just a thought.
I dunno. I changed my first name for reasons unrelated to gender. I don’t like being asked about my birth name, and I don’t like the implication that it’s somehow the “real” name. When the concept of “dead names” was explained to me, I understood it immediately.
I did as well, at the ripe old age of 35.