Question regarding percent hydration for 100% whole wheat bread dough
It depends a bit on how coarse or fine your wheat is ground. 

With 75-85% you are in a pretty mainstream range - the equivalent of 65-75% hydration in white flour recipes. 

If you work with longer or multi-step preparations (cold rise, bigga/levain/poolish methods, sourdough...), you can push it towards 100%, like for the no-knead-bread here. 

As a rule of thumb, go up by 10-15% when switching to whole wheat (less if mixing).

King Arthur flour supports this when writing 


  The hydration (weight of water compared to flour) is 75% in this1 recipe for No-Knead Crusty White Bread. But since whole wheat flour absorbs more liquid than all-purpose flour, we’re going to increase the hydration in this recipe to 85% to 90% or so.


in their recipe for whole wheat no-knead bread.



(1 the original recipe with refined flour)