I suspect the point to your walks is for his exercise, so, if he has no physical reason to be unable to walk, you may need to help him think compliance with what you want is his idea...LOL. Maybe try giving much loved treats to him and Summer but only for such things as coming to you/putting the harness on, and taking steps forward while on the lead. He may have created a 'game' out of the 'catch me if you can' when you first were trying to put his harness on, and if so, may enjoy his game more than you think.
Does he seem fearful when walking? I know mine sometimes bark at shadows, or when they see the 'monsters' (trash cans for pickup...LOL) in the yard. They have even fear barked because the monsters from the night before have disappeared tonight...LOL. Go figure, huh? When that happens, I take them...carry while tightly hugging and talking soothingly and explaining to...them so they can inspect the suspicious object. He could also just be a homebody.
