You have way too much gain. And the volume control in the D100 is digital domain, so anything below 3/4 and you run the risk of "bit stripping" the music
Your Primaluna input sens is about normal, and high impedance. If you use the fixed outputs of the D100, they are 1/4 the level of the variable.
You could then use a $49 Shitt sys and run the fixed output of the D100 and use the Schitt's level control.
Or using the variable out you could turn it up full, then for the loudest you want to hear and adjust the Shitt to that level, then you can still lower the remote level up and down but you’ll be using it the top 1/4 of full. So no "bit stripping"
Don’t bother with those inline attenuators, I’ve haven’t heard any that sound good.