As for 4G (or more), the nvidia driver doesn't seem to support PAE. My mistake. It was my windows boot that was successfully using PAE, not my FreeBSD install.
But on to Zander's request. I've create two nvidia-bug-report.log's --- one with DFP0 as the metamode hint and one with DFP1. They seem to behave slightly differently --- so you might want to have a look at them.
They are, however, too big for the forum upload facility, so I'm leaving you two links here --- you can fetch them yourself from my website: