Amherst2019 - I understand your concerns. You have done a fair amount of research, but I would characterize it as in the realm of anectotal, which is valuable to some extent, but can be dangerous if it is the only thing you do.
One thing you can do is to learn as much as you can about the current president (this is Biddy Martin, I looked it up). I personally believe that the leader of the institution can make a big difference over time. To some extent I agree with the poster above. Any changes to Amherst, real or perceived, will not happen precipitously (1-3 years). But the leader(s) of the institution can make a big difference in the long term trajectory of the school. And once that trajectory is changed, it takes a long time to reverse it for better or for worse. Think of the metaphor of turning an aircraft carrier.
President Martin has been there going on 4 years. So if she does a decent job, you can expect her to be president through your period of attendance and at least 4-8 years beyond. What is her vision for the college? How about the trustees or governing body? What is their vision and how harmonious is it with the President’s? How does the strategic vision for Amherst square with what you believe to be important the next 25 years in society in general and higher education specifically. How is she at fundraising? What are her relations with the faculty and students? And so on. If you start getting a good feeling about these things, than you can be reasonably assured that Amherst will continue to occupy a position among the top 5 LAC’s for the long term (20 - 25 years).
Beyone the above, it sounds like you found a lot to like during your visit to Amherst. This is powerful first hand information. Try and search your thoughts about the visit. Were they real and sustainable feelings? Are you too affected by a gauzy view of LAC’s in New England? Or do you feel that you saw what will be real about Amherst for you the next 4 years? If so, then you are probably well on your way to choosing Amherst.
One last thing. Are you and your family okay with the commute from CA to Amherst, financially and time-wise?
Best of luck to you.