Try out a variety of different fats, I will eat the whole animal so I get, backfat, suet, intestinal fat, bone marrow, brain fat. Then I also use coconut butter fairly heavily. I estimate that about 70 percent of my total calories come from fat.
Supplements should not be necessary once you begin to get the optimal balance of nutrients from raw animal sources.
My stools are well formed and digested. I usually have one every two days.
Occasionally I will have some type of huge movement due to to many eggs or whatever, and I will go up to three days. Because I am on a 90% carnivorous diet there isn't enough bulk to prompt daily bowl movements, so I try not to worry.
Instead of using magnesium try of few whole raw eggs everyday, if you have issues with constipation, or even just a splash of coconut water. Both eggs and coconut help provide good a mineral balance and have a slight laxative effect.