1. I could definitely see this working as an adventure game. Since all of the adventure game mechanics and the kid talking to himself, will all be a part of his insanity, and probably creep everyone else out. I'm not so sure about the "regaining his sanity before hurting his mother" bit. It sounds like it would be much easier and more entertaining for the whole game to be about him slowly losing his sanity, until you accidentally hurt your mother and then snap out of it. You could slowly increase the game mechanics you have access to, to show the loss of sanity. And if you could get the player to kill the mother without realising it until it's too late, then you'll have a great game on your hands.
2. It would probably be annoying having the character constantly not want to do obvious things because of his germaphobia. Also, I wouldn't want to imagine the amount of detail you'd have to put into the backgrounds to make them all look filthy.
3. How exactly would the kitten "power up"? Point and Click adventure games don't tend to have that feature. Instead they'll just give you more inventory items to work with. I guess you could give more commands to use. But overall this sounds like it would be a very long and linear adventure. Which could be just what you're looking for.
4. Sounds like a perfect plot for an episode of The Twilight Zone. It just needs a twist ending.
5. I like the sound of this one, but does it have to be about the boy stopping his grandparents from losing the farm? I think I'd rather much more enjoy a "Coming of age" story, where it's about the boy learning to live unplugged, getting new friends, something bad happens, and he then leaves more mature. You know, rather than the kid movie tropes which usually involve a couple of bumbling bad guys that would gladly murder a child (have you ever noticed that in those types of films?).