Cats are quirky and can have many reasons to do that. If she is an older cat she may have arthritis and the walls of the box could be high for her to easily get over. Some cats hate covered litter boxes. If you changed litter brands recently she may not like the texture or smell. The box could be too small; I bought a large metal litterbox for mine before they quit peeing over the sides on the wall.
Emotional issues can cause outside box use too: new pet, roommate, someone moved out. All can have an effect.
Feliway has a pheromone spray or diffuser you can use that is supposed to help with issues like urinating outside the box which may help with the poop problem. Another brand called Comfort Zone has a “spray and scratch” that’s slightly cheaper.
If the vinegar or peroxide that others recommended to clean the potty spot don’t seem to do the trick, then you can buy an enzyme cleaner like Nonscents “stain and odor eliminator” to see if that will work.
Not sure what’s available where you’re at without a prescription, but I recommend Orajel or any equivalent ulcer/tooth ache gel.
In addition to the other things you’re already using, you can steep black tea bags in warm water and gently bite on that. The tannins help with bleeding and inflammation.
A mouthwash or spray with Cetylpyridinium Chloride in the ingredients list will help with healing, but don’t buy a mouthwash that has alcohol/isopropyl in the ingredients. Dentyl, Oral B Gum detoxify, Parodontax, Biotene Dry Mouth Spray are all good.
I had several teeth removed from my inside my jaw that never came out and had a bone graft placed in the area that had to heal for 6 months before dental implants were placed. The mouthwash definitely helped me heal faster from that surgery than when I had my wisdom teeth out the year before and didn’t use any. Just do a gentle rinse dont swish it around hard! You don’t want to disturb the blood clots and get dry socket.
I hope you start to feel better soon!