I think that setting the shutter speed to 1/320 sec. auto FP mode would not be a good idea.
First FP mode and Manual flash control don't mix. Second, the D700 is capable of up to 8 FPS with the MB-D10 and an EN-EL4(a), or AA batteries at a shutter speed of 1/250th sec. or higher. So 5 FPS should be no problem. To get the maximum FPS rate, set Custom Setting a1 AF-C Priority Selection to Release and use Continuous AF mode or use Manual Focus mode. Three, the short flash duration should freeze any subject movement as long as the flash is providing three or more stops over the ambient light level.
I think setting the on camera Speedlight to Manual M 1/128 (Not Commander mode) and your remote SB-910 in SU-4 Manual flash mode to M 1/64 should get you a decent burst at 5 FPS. Using SU-4 mode should eliminate any communication delays between the Commander and the remote.