Get an automatic litter cleaner machine. This might do the trick. It appears that your cat does not like the odor of his pop. If that is too expensive get him several litter boxes throughout the house and use the odor cover up type of litter. Ask the local Humane Society or Flock at Petsmart for help as well. They might have better answers. Sorry this took so long I haven’t been visiting for over a month. CSINBAD.
If he is going in the same place outside his litter box. It could be you are using a litter is is not sure about. Try switching litters to scoopable it is smaller grains and cats seems to like it better. Also if it is the same spot he goes in outside the litter box then he has gotten the odor there so thinks he is suppose to go to the bathroom in that spot. Put a mixure of vinegar and water in the spot let it air dry and he should go in the box. The vinegar and water gets all smells cats leave that we can’t smell.