Calcium supplements tend to mess up my gut. Most supplements do. Do you just add salt to food or take salt capsules or just put a little in mouth throughout the day and let it dissolve?I was in your position. What helped my digestion was a round Peat's flowers-of-sulfur protocol (in case it was SIBO) followed by making sure I ate a carrot every single day, away from other food. Also, I didn't do well on milk so I used an eggshell calcium supplement (I use a really good one from Amazon but now it's not available for some reason). The calcium is really important for digestion. Also, I would only eat bulky foods once a day (dinner). Now I have transit time of about 10 hours or less. I just can't seem to lose weight so take my words with a grain of salt (pun intended, I'm seeing nice improvement by having 10g of salt per day).
I also saw a boost in my health when I used high dose vitamin D (20k IUs) for a month. I'm assuming I was deficient or have some infection blocking absorption.