Write your LOCI including the things you mentioned. You might reiterate how you will specifically engage with the Columbia community, which I assume you did in your supplemental essays, but it’s ok to highlight a few things again…like a class and/or research with a prof you’d like to be involved with and/or a club or two you would join and why. I would not presume to tell Columbia why they should see you as a good fit, rather show them with specific examples.
I believe you attend a private HS? If so, do your GCs call college AOs on behalf of waitlisted students to advocate for them? If yes, ask if they would do that…but only ask them to do that for one school, it’s not ok to ask your GC to call multiple schools telling them you will enroll if admitted.
After these activities, please deposit at a school you have been accepted to by May 1, and get excited about that school. Good luck to you.