>>2954034ahhh glass....there's the problem. I tried that early on and it caused all kinds of problems with reflections. You gotta ditch the glass. I found absolutely no way to use glass without reflections ruining the scan. Try just laying the negative on your light source for now, until you can get a holder. Yes, you might get distortion, but you won't get reflections...which are worse.
Micro-Nikkor 55/3.5. Excellent lens. Same lens I am using. It should yield you excellent scans. I use an a6000 with magnified live view to focus. Not sure how that works on your d700. Also I tether through Capture One, and it works very well.
>>2954050The yellowing is due to uneven backlighting, most likely the glass problem I mentioned above. Try one without glass, ignoring distortions from the curved negative.