Re: the scratching. Do the doors have doorknobs? There are "scratching posts" that you can buy that are long flat boards with sisal wrapped around them that hang from a doorknob. I don't know if Kermitte will scratch on that as opposed to the door itself, but it's worth a try. It'll save your door and lower the volume of the scratching to your ears. Is this a behavior she just started or always had? If it just started, it'll probably stop after a few weeks when she finally accepts you're not opening it for her.
As to the window, I have no suggestion. Our cats paw at and try to "climb" the windows when there's birds or squirrels or something going on. Fortunately it's not noisy.
Re: Elmo. Purchase a curry comb. If he doesn't love being brushed now, start slow with him. Our cats hated the brush at first, then tried to chew it - and now beg to be brushed. Actually, it's really good to brush both your kitties every day. You'll be amazed at how much hair you'll catch on the curry comb instead of your furniture.
And if he's eating that much hair, I'm not surprised he's getting sick with hairballs! If you don't want to vaccum so much, those tape-lint-rollers are great. Is there a Bed Bath & Beyond store near you? Or maybe they sell this in a pet store near you. It's the tape rollers called "Evercare." They DO pick up more hair than other ones!
The other thing you can do, if you have the time, is grow "grass" for them (kitty grass is actually oats or oats & barley). We have small trays of it, and we plant it every three days to keep a fresh crop going for them. Tuxedo has longish hair, and constantly had hairball problems - but the hairball remedy stuff or treats just gave him diarrhea. Some have had great success by adding a tablespoon of canned pumpkin to a bit wet food for kitty once a day - we never tried that, but have had great success with the grass. We just leave it out and let them graze at will.
The other thing I would do is take Elmo to a vet and get a complete blood work-up. Tuxedo used to eat litter all the time, and after bloodwork several vets said he had no mineral deficiency or anything, so just ignore it, it can't hurt him. Months later he became very ill. We ended up at a feline internist specialist. Tuxedo was so anemic he was near death. We told the specialist he'd been eating litter, and he knew it was anemia right away. Turns out that most cats that have anemia eat litter. Tuxedo developed it over a long period of time, but we didn't know eating litter was a symptom of anemia, so we didn't check his blood frequently, and planned only on normal annual vet visits.
I've never heard of eating hair being a symptom of anything, but you never know. I'd get a full blood work-up done just to be on the safe side, and I'd watch him for any behavior changes. With Tuxedo, he just slowly became more and more listless - the change was so subtle we really weren't sure there was a problem. So just to be safe, get a blood work-up done, make sure everything's ok, and keep an eye on him. And adding a bit of canned pumpkin to wet food once daily or growing them kitty "grass" might help too. Might even stop the hair-eating problem.