The paper base if unexposed is as white as it will be. Change to off white matts or use a paper with a whiter base.

To compensate for drydown, make a print that looks good wet but squeeged with a 30 sec exposure by adjusting the aperture only. Then make samples at 29, 28, 27 26, and 25 sec. One of these will look good dry. 4x5 is all you need. Now you know the percentage dry down to apply to that particular paper/developer /toner.

If you are math challenged, 27 sec is a 10 % reduction , 28.5 would be 5 % reduction.