Perfect endings, LGBT+ or otherwise, tend to feel contrived and implausible. Ending on the upbeat, on the other hand, strikes me as a great way for your reader to walk away feeling good.
Sure. It’s a scary thing when you want to be inclusive and not upset anyone. But I think the trick is basically to have a character who just naturally is whatever, rather than trying to glue a label on a character and then force their behaviour inside a textbook list of criteria and behaviours and stereotypes. Labels have fuzzy boundaries and people step between them as they evolve and don’t always fit cleanly inside one or another - that’s why they keep proliferating. Obviously researching some basics is essential. But I’m cis and I’m writing more and more trans characters of varying flavours as central characters, and I’m assured by trans folks that they work fine.
Basically, not everyone who uses a given label will have exactly the same experiences, feelings, perspective, and so on as every other person who uses that label, so just make sure it’s plausible and consistent for that character and doesn’t include outright errors or stereotypes. It’s generally not that hard to find someone who does identify as whatever label.
This. Lots of this. ALL of this. Characters who are more than their labels, to themselves and to others.