Welcome to the thread!
In regards to your LOI question, I sent update letters to all the schools that would accept them about a month ago, and nothing really has happened except not being rejected from schools that have sent out rejections. I would say though that in your case, it is going to be a wait until the bitter end because your numbers are on the low side, but it could be helpful to send an LOI/update letter maybe. I have a low GPA which I think is my main issue, but my MCAT is very good and I mainly got IIs within 3 months of being complete at these schools.
When were you complete at most of these schools? Maybe they just haven't gotten to you yet.
I don't want to burst your bubble, but Vandy most likey will not send you a secondary (based on previous threads), I should've known better to apply there myself. Also, if you're not a NC resident, the chances at UNC are also slim. With your other schools, were your numbers in range for these schools? I know 23 schools is a lot, but I applied to a wide wide range of schools and am glad I did because I got interviews at places I thought I never would and rejections from places I thought were a match. This process is so weird, so so weird.
And I have to throw this out there as an MCAT instructor, but a 7 in VR could potentially be a big red flag. Playing devil's advocate, but do you have it in you to take it again and boost that score? Not to cast doubt, but in general though, in the event that you'd have to re-apply,that VR score would be something to improve, and then you'd be looking at the new MCAT with new content and it's longer. Just a thought, not trying to cast doubt, but I am one to look at all the possible scenarios...