Practice is almost everything in that field. I did also much practice in German writing over the years, it's just that this one is my first actual story in full English.
It shows, nine or ten years ago I have written like that too.
If you want to change it go ahead, but you don't need zo adhere to the new canon material just because it's there. If your story is from the time that, let's say KH 2 was the latest canon entry and your story is already finished and coherent, you can also choose to diverge from the canon and just tell the readers in an author's note that the story follows canon only up to KH 2 or something. It's the same with my story which follows the canon up to the end of Re: Coded (or rather, Blank Points) where Sora decides to venture out another time to save the tormented. After that though my own plot kicks in and Hearts in Unison will completely disregard anything from Dream Drop Distance, also because I had the core plot planned out before DDD was even out in Japan. There are some similarities nonetheless especially regarding hearts since I had some ideas which are pretty close to what DDD actually has shown us.
The difference is that my story contains no original characters (meaning characters that I have invented myself). If you create an own character and place him/her into the KH-Universe then you already diverge from canon by adding someone who wasn't really there. A self-insert is also a form of this since the included original character actually becomes the avatar of the author him/herself.
I write myself in Word, although the formatting isn't always kept when I copy the text into the forum.
I have no problem with that. Feel free to ask away. ^__^
However, as you might have noticed, my answers are sometimes pretty delayed which has 1st to do with my timezone (Europe) and 2nd because of my limited time during the week since I have a job to attend to.
I'll try to get back to people as soon as possible, but sometimes the evening time simply isn't enough to answer everything. <__<