The Fujinon 250mm f/6.7 has a good reputation and lots of movements...it's something of a cult classic lens. I've never heard how it performs wide open, but if you can find one for a reasonable price you're pretty much guaranteed you'll be able to sell it for about what you paid for it if it doesn't work out for you.
I don't really have any great info for you regarding lenses, but one thing I wanted to throw out is that a bright flashlight is a great aid in nighttime focusing. Depending on your subject, you can find someplace to lay it on your camera body, or if your subject is accessible you can just walk up to it, put down your flashlight, and head back to the camera. I have a four D cell MagLite that throws a lot of light...very handy for focusing at night.
One other quick thought regarding lenses. I have a JML 8-1/4 f/8 process lens that's good wide open. Since you're shooting on B or T anyway, using a lens cap in place of a shutter isn't too much trouble. The lens has plenty of circle for 8x10 with movements. Mine's razor sharp, and I got it for very little money. You're looking for a longer lens, but JML made a lot of lenses over the years and I'm sure they made a number in the 10" range that have good coverage. A web search will probably help you out. (The JML web site has a chart of a whole lot of process lenses they made over the years, including the coverage angle of the lenses. If you find a JML lens that you want more info on, chances are you can find it on their site.)
Best of luck.
Dave