Problems With My Papillon. Please Helpp?

Boomer my papillon is a pure bread dog. Or so I though… When I got him, I was told that he was 18 months, and when I took him to the vet, I was then told that he is closer to 3-5 years, and also imbread back down the line.. something with his grandma…
I fell in love with my boomer, he is so sweet. I asked a question before about him, because he is hard to train.. I was told by a dog trainer that its the imbreeding.
Now my problem is he doesn’t quite understand his toys. Isn’t sure what to do with them.. He would will run and play keep away from me and my boyfriends kitty. And he will play with our clothes, anything he can find. Sometimes he will run in the bedroom and come out dragging a shirt thats twice his size. He couldnt care less about a ball, chew toy, rope toy, or anything…. just clothes.
I tried smaller balls to fit his mouth better, but he just doesn’t care.
How do I get him to want to play with his toys, not chew my clothes…