Re: furniture
I think the way to think about it is that cats have a need to scratch. They must do it, so they are going to scratch the things that seem most natural to them. Big sturdy things that don't "give" when you put their weight on them, and then smell right and feel good to scratch, and in convenient, "socially significant" locations (because they are also depositing their scent on the things they scratch).
So here are your choices:
1. Provide them "approved" things to scratch that will be more attractive to them than what than the furniture that you would rather they not scratch.
2. keep their claws trimmed, so there is less of a need to scratch, and when they do, it will be less far destructive
3. Put the furniture somewhere where they can't get at it
4. Replace the furniture with more "cat friendly" stuff that is more resistant to scratching, and you're not going to freak out about it as much.
5. You'll inevitably need to compromise some. If nearly every piece of furniture in your house needs to be a "no" place for cats, you really should re-think having cats. For example, I have one really nice, expensive, extremely comfortable chair that is my "work chair" in my home office room. Serafina loves to jump up there when I'm working, and "perch" right by my head. It's nice having the company, and it's very much "her spot". Downside? It gets scratched up. It's ok, not gonna fight that, as I'd rather have a cat there, then have a prestine chair top.
Ideas:
a. I've had a lot of success putting nice "cat approved" scratching posts right next to furniture that I'd rather them not scratch.
Something like this:
https://smile.amazon.com/SmartCat-3832- ... ching+postb. Cats often will scratch the heck out of cat trees bases, provided they meet their criteria. It's funny, some of the trees that I have, I've had for over 10 years, and are for the most part still going strong and in good shape, but I'll probably need to replace some of them soon just because the bases have been completely destroyed by cats sharpening claws. That's ok though, I want them to!
c. You can make any individual surface less or more attractive to a cat by manipulating the smell. Put catnip on the "yes" places, and bitter-yuck on the "no" places.
See other threads on cord chewing. That can be really dangerous for the cat, and really expensive for you. Better to put electric cords in cord protectors, and spray with bitter yuck. Once they are "trained" to dislike chewing cords, you can probably get rid of the cord protectors.