how many schools should I apply to?

First of all there is no rule of thumb that is valid across all applicant types. Some extremely confident students who are recruited athletes, legacies, children of faculty just apply to their college of choice ED or EA. If they get in, they are done.

A few cycles ago, a lot of college advisors and HS counselors were using some sort of variation of applying to 3/3/3 or 3/6/3 or 5/4/3 or other mixes because there was a clear differentiation between traditional hard reaches like Ivys/Elites versus 2nd tier highly competitive schools. So maybe reaches were schools with admit rates between 4-10%, hard targets 12-20%, targets 25-40%, safeties, 50% and above published admit rates. I'm not talking about CV derived rates.

No there are close to 50 schools with admit rates less than 10%. So it's very messy. For example NorthEastern had a 7% admit rate last cycle, and Georgetown 11%, Barnard 8%. But clearly GTown and Barnard are much better schools. So you might think NEastern is a target but unless you apply ED, the admit rates are horrendously low. So they are really a reach school these days. Would I want to pour a lot of time and effort to get into NEastern personally? Absolutely not. I'd rather go to BU, BC or Tufts if I were keen on being in Boston.

Looking at your list, I would recommend looking into Mount Holyoke, Skidmore, Bennington College, Bates, Trinity College and Connecticut College as well.

Personally, I think if you spent some time actually visiting these colleges in person and going on campus tours and info sessions, you will curate a better list for yourself.

Good luck.

Sixteen is actually a really good number, and since you (probably) won't get accepted to all of them you'll have less than sixteen to choose from. However, if you're looking to narrow it down, here are some things to consider: location, size, majors, atmosphere, graduation rate, etc. Also visit the campus to see if you like it (that relates to atmosphere). However, you seem to have a good amount!

I think that you should apply to as many schools for which you can come up with a quality application. Sometimes college applications can be a matter of luck, so applying to many reach schools in that regard can help boost your chances of getting into one of them. Something you can do is prioritize which colleges you would actually really want to go to and apply early action to as many of them as possible (you can get started with the essays and everything this summer), and continue to work on applications for targets that you truly see yourself going to for the regular decision round. With the safeties, I personally would work on the application last so if I get a acceptance from a target or even a reach in december before working on them, then I wouldn't even bother finishing them.