This is the 80-10-10 concept; I believe it is reasonable for now to aim as Fuhrman above talks for 70-10-20 or 60-10-30, where the last number is calories from fat, the smallest - protein.
It is OK if you are already into the short fast. I meant, given your history, it will be easier on you to first clean your colon and then do a longer fast, if you decide for a longer one. Short fasts are not so critical in terms of cleaning the colon. Still may promote better function if you do it right.
The swelling under your left rib cage may be just stool stuck in the natural bent of the colon between the horizontal and descending part. Back aches is often experienced during fast and is not necessarily related to digestive health.