

Probably a capybara, or a cheetah. Both are rather chill animals, and cheetahs are fairly able to be domesticated (and have been multiple times throughout history) at least compared to other big cats.
Both are still a really bad idea, and the latter will probably result in injury or death. After having interacted with two Cheetahs through a rehab centre, I’d be open to try.
Because we love em!
Scratching in the “wrong” places tends to be either from frustration, or a lack of stimulation/appropriate places to scratch.
You probably already have some scratching toys/mats/spots, but try experimenting with different orientations; attached to a wall, 45 degree angles, those wave pattern ones, not just straight flat on the ground.
Also, try different materials. Some cats love that rope, others want cardboard, and some are very picky or want both.
If your cat is overweight and leaving streaks or not drinking enough, you should talk to a vet, ideally making an appointment with a nutritional specialist. It may be they are allergic to something in their food, causing intestinal upset. If that’s difficult, you can also simply try giving pouches of small gastrointestinal wet food and seeing if that helps.
It may also be because they are too fat to clean themselves properly, and they butt-scoot to clean it that way? You can get special diet food that fills them but doesn’t have as many calories.