Thanks for the response FurryNutz! I've tried searching without much luck, so I'm glad to hear this can be done.
According to the 192.168.0.1 configuration page, I'm on "Hardware Version: A1" and "Firmware Version: 1.04NA". I'm in Colorado, USA - is there a more specific region you're looking for, and if so where would I find it?
Edit: The physical router says 1.01NA, which I now see probably is North America for the region. I don't recall updating the firmware from 1.01 to 1.04, but it's possible I did a long time ago or that I might've gotten the router secondhand. I honestly don't remember!
Cutting off all internet access overnight is perfectly fine. Ideally, it'd be nice to leave access to a couple sites so the DVR can update program info, but if that's not possible it's a tradeoff I'm willing to make. Just as long as it comes back when the router schedule period is over the next day!