On recent-ish versions of evince it is possible to do a bit more via dbus. For example, forward and reverse synctex search between evince and vim over dbus is done at [1]. I use this when I use evince, but I acknowledge that it has stupid flaws.
Having written this, I am actually completely incapable of retrieving the page number over dbus. (As you had mentioned). I'm a bit surprised that forward and reverse search can still be done.
[1]: https://github.com/peterbjorgensen/sved