1. Compressor: DV/DVC Pro
Should I go to Pro Res?
You should stick with the format you brought the material in for best results, so if you're using DV then leave at DV. The only reason you'd want to change this to Pro RES is if you've converted/captured material at Pro RES or have a number of different formats within your timeline.
2. Video Processing: Render in 8-bit
Any reason to change with DV source material?
8-Bit is fine for DV, you'd only really need to go to 10 bit if you were working on uncompressed material or anything that might be leaving your timeline for further compositing.
3. Motion Filtering Quality: Normal
Should I change to best?
This can be left as is unless you're going to use the motion tab for resizing or positioning of the clips in your timeline, and even then I've not really noticed much of a difference with DV material myself.
4. Render Codec: Autoset at ProRes 422 [HDV... only]
I'm not entirely clear why FCP would autoset to that when I have no HDV material.
This is a setting purely for long-GOP material (HDV and XDCAM) and won't have any effect on your DV timeline.
As a rule of thumb, everything FCP does to your timeline with the setting will be fine. The ideal workflow would be to keep the footage in it's original format for as far through the process as possible, only converting from the timeline once the edit is complete.