Obsessive Behavior!! Please Help!!

It sounds like a classic case of being seperated from his mother too young. Kittens learn literally everything there is to know about being a well-adjusted cat from their mothers. The mother scruffs the kitten when the kitten is being bad, teaches proper litterbox usage, and provides comfort for her kittens so you don't end up with a nervous, skittish cat after the kitten is weaned. The food aggression is something that Cosmo's mother would have scruffed out of him if he had been allowed to be around her longer. My kitten was very aggressive about food, but he calmed down over a couple months (and a couple fights with my other cat who put him in his place), and now I can free feed without worrying about the cats fighting.

 

As for the litterbox issues, I think that you should consider getting a third box. It's usually recommended to have one more box than you have cats, just so issues like this don't arise. Cats will often choose one litterbox to pee in and another to poop in, so that isn't too strange. It does sound like Cosmo is particularly anal about his pee litterbox, and he is trying to get Grizzly to conform to him. A third box would give Grizzly his own while letting Cosmo have his two seperate boxes. I'm sure that Cosmo will become less OCD as time goes on and he starts to warm up to Grizzly, but until then all you can do is make sure both cats have enough resources so they don't have to share anything. Cats are very territorial, and i think it would make the adjustment time go quicker if they didn't feel like they have to compete for a finite amount of resources.

 

Also, in my experience, some cats are just weird about their litterboxes. I have known cats who sprint out of the litterbox after pooping and will run around wildly for a few minutes. Other cats spend multiple hours laying in their boxes or digging around in their litter.

As for the food aggression, I've had a few kittens at different times (have a cat rescue) that were food aggressive.

From what I have found, if the kitten had competition from bigger/more pushy littermates, it will make for a food aggressive cat, which will eventually die down pretty much, once he figures out that there's nobody that will take his food.

I have had a bit of success helping kittens overcome food aggression just by leaving a HUGE bowl full of food out all the time. Once he sees that there will always be more than enough food he might calm down. . .on the farm he probably had to fight for every bite. I don't know how your older cat does with free-feeding but it might work, and when he's older you could phase out the free-feeding gradually.