Oh that sound like a nightmare. Does he hoard stuff? Why is he collecting car parts? Could you give him an ultimatum? Like, "clean up all your clutter in 2 weeks or I'm hiring a skip and will start chucking whatever taking up living space!". That's what I'd do. You and the little ones need and have the right to enjoy some uncluttered space to live and play. No wonder you're not feeling unhappy and frustrated.

Can you see things improving or able to improve? What things about your partner and relationship did you used to enjoy?