I resolved my IBS starting at 3 months carnivore , but it took a year for full healing. I am currently eating like you, at 80% fat and restricting my protein for me. I am still eating more protein though at over 2g/kg body weight.
I am sorry to hear of your struggles and unfortunately I have little advice. I have been eating tallow with my meals, and find it easier than liquid bacon fat, but hard bacon fat is better to digest for me.
You may want to look at adding sweetbreads into your routine and tongue due to high fat content. I am always wary of sausages since many have carbs mixed into them, and spices which I avoid.
Most carnivore forums suggest just steaks, no organs. I am alone in most places as I eat organs daily and feel that is the healthiest way to eat, within moderation. Here is my plate last night, the white is tallow made from Buffalo and beef heart fat that o tendered.
Lastly, have you considered heavy cream as a fat source. I find I have no stomach issues with this liquid fat form and love it as a pure fat form of cheesecake every once in a while.
Hope you can resolve your issues.