Another major to consider would be Cognitive Science, which spans psych and neuroscience as well as adjacent fields like linguistics, philosophy, and computer science. Pomona and UCSD have strong cogsci departments.
Since you like Pomona, have you considered any of the other Claremont Colleges? The Pomona CogSci major is available to Scripps students, and Scripps has its own Neuroscience major and strong premed advising (they have a postbacc program in addition to the usual undergraduate premed population). You could potentially get up to half-tuition merit from Scripps, whereas Pomona does not give merit aid at all. (The cross-registration is seamless and widely utilized, so the only truly single-gender classes at Scripps are the three semesters of humanities Core.)
There’s a huge need for psychiatrists in general, and for those who are committed to addressing inequities in particular. The one thing that strikes me, though, is that if you choose a path that leaves you with a huge debt load, you may find that you can’t afford to work in the settings that serve the people most affected by inequities. The financial freedom to do what matters most to you is something to take seriously. You seem like someone who could attend virtually any reputable school, and get to where you want to go from there.