It simply sounds as if you've written a good short story/novella. Put it away and move on to the next piece. If expansion is needed the MS will call when it's ready.
I think alot of wannabe writers, myself at the head of the queue, get worked up on the minor things like word count, ms format, font etc etc, without giving the work itself the room and time to breathe, develop, to find its own way into the world.
Breaking into this game is hard enough without restricting ourselves and forcing a piece of art into a specific pigeon hole" If it gets that far, let the editor/the agent/the publishing house ask those questions!
My WIP will, tonight, when i get out of this office, off the train, home, dinner with girlfriend who feels like she's been abandoned out of the way, hit 200,000 words. Five moths ago i envisioned a 3 month, 125,000 word period for the first draft. I was wrong. I worried myself into aborting the work where it stood a month ago and writing the end when i shouldn't have. Now I just let the story write itself to conclusion and, lo and behold, I will be done by Sunday.
If an editor likes a novel, they will take it, regardless of length. (Disclaimer: Genre specific writers of works, with strict guidelines on length, Romance etc, should ignore that last comment!) They will see something, a talent, to work with, end of ,simple as.
I know every writer is different, but I'm not sure about the letting it all flow and then going back to fill in the blanks theory. I've read some fiction in which this is obviously the way in which the writer works. In one novel, can't even remember what or who, the writer felt the need to tack on to the end of every chapter a 'reaction' paragraph. Every single chapter. Pulled me out of the story, I lost confidence in the book and found something else in which to invest my time.
Descriptions, colours, emotions are as organic and influential as dialogue and action. Take time, work those things in as best as possible. 'Going for the Money shot' is the phrase i'm thinking of! Of course there will always be some blanks to fill in, some points to clarify, but remember, writing a novel isn't a race. Take the time to craft, as opposed to just writing. I'd rather take 6 hours to write 2000 words of good prose than I would 5000 words in an hour of he said she said they did they kissed they ran into the sunset kind of thing, but that's me, that's something I learned through the 200,000 words of the first draft of my first, still on submission 5 months later, novel.
Just my 2 pence worth! Good luck.