Congratulations on being admitted to such a large group of good departments. This isn't my area of research, so I can't comment on that aspect of fit. But please don't let the size of the stipend influence your decision. A program that is a good fit for you repay itself many, many times over.
I think your other criteria are spot on. I would reach out to a handful of current students at each school -- the DGS can put you in touch -- and talk to them about their experiences in the program. Ideally students persons who work in your fields of interest. That will be your best data on whether the department is friendly, supportive, and has a lot of faculty-student interaction. Ask them what they like about the program. What they don't like. Are they happy there. What do they know know about graduate school that they didn't know when they were comparing options. Also ask them about which faculty students enjoy working with, quality of instruction, etc. You don't want to show up and then find out that the professor who teaches development is a jerk who students avoid.