I have/had an indoor cat that is/was a terrible clawer upper of stuff. Here’s the weird thing: he won’t claw leather furniture, only fabric furniture.
Anyway, I also adopted some barn kittens about the same time husband’s co-worker gave us indoor kitty (her new baby was allergic, and my old indoor cat had just died). I thought I had 4 female barn kittens, but there was a male in the bunch. I had all of the kittens fixed ASAP, but the male is aggressive to the females and roamed, even though he was fixed really young.
I started bringing male barn kitty indoors during the day because indoor kitty (also male) is bigger than he is, and doesn’t take crap off him. That way I didn’t have to scour the neighborhood for him at night, when the coyotes come out (I shut the barn kitties in the barn at night … and yes, they have a climate controlled tack room to sleep in!), and he couldn’t attack his sisters all day. Male barn kitty has to go out to the barn at night because he is too nocturnal… he wakes me up with his meowing or jumping on me (he likes to smack me in the face with his paw at 3 am), and I have a hard time falling back to sleep… so out he goes. He’s twice as big as his sisters, and he will take on pretty much anything that digs or tunnels its way into the barn, so he earns his keep killing rodents at night.
After I started bringing male kitty in the house, I noticed something almost immediately. Both cats were pooped when I got home, usually sleeping on the back of the couch together. I will say there are generally large piles of ripped out hair around the house, but no blood. They both wake up when I get home, we play laser pointer or feather toy for a half hour, then they go back to sleep. Furniture has been left alone.
I know you don’t want another cat, but somebody to play with might be helpful. These cats tear around like crazy, jumping up on top of the kitchen cabinets, up and down the stairs, chasing and wrestling, and they wear each other out. If that doesn’t work, maybe if you play with him hard for 15 minutes morning and evening, that might take the starch out of him?