"For me, a ‘partner’ would be probably be a serious, committed relationship of eighteen months at a minimum, where you’d declared love and signalled commitment, met one another’s children, friends etc."
Interesting because I'd still think boyfriend and girlfriend for that if they still lived separately (apart from those 'living apart together' people).
"I wouldn’t even think a three month relationship that involves seeing one another once or twice a week was even at the ‘boyfriend/girlfriend’ stage yet"
What are they then? They're not friends, they're not friends with benefits because they're exclusive and in a romantic relationship. You're the second person to say this in the thread and I find this to be quite a worrying modern trend for people to be in relatively serious relationships, going out together but somehow not boyfriend and girlfriend?
"far less involving ‘support’ — don’t you have friends and family for that kind of thing?"
Not everyone does, no. My family's abroad and friends are not necessarily emotionally close. And frankly the boyfriend has a closer relationship to OP than either friends or family so I don't really get the logic of saying she should be relying on them rather than him.
"Having said that, I’m fussy about articulate written communication. I’ve never fallen for anyone who wasn’t clever and eloquent in writing, whether that’s text, letters, email etc. I’d find formulaic messages, poor SPaG, or text speak a total turn off."
I wanted to say you're being silly with this, but I found someone I used to have a crush on years ago on FB and realised that if we'd been FB friends at the time I probably wouldn't have fancied him! So yes, we want what we want!