I focused on the part where you said he goes a little in the box then finishes up elsewhere. Could he just be constipated? At age 8, he is considered a "senior" cat. I find my MATURE felines need a little more water in their diets, and I give them canned food twice per week rather than once per week.

All but Chestnut. Chestnut has had a tendency to being constipated all his life. So I give him the heirball remedy twice per week to keep him regular. The other cats get that hairball stuff once per week, for controlling their hairballs nothing more. If I skip a midweek dose for Chestnut, I know it in about 3 days!

Just a thought.
Good luck.
Sandra