Hey James,
Hopefully I can answer just a couple of your questions here as I am not a Porper Clip expert. I hope someone with a deeper knowledge of Porper Clips will jump in later and answer your questions more thoroughly but I will try and help the best I can.
I have a Porper Clip (not a Dan and Dave Carbon Edition or Dan and Dave Clip in general), but I do have an original Porper Clip so I am basing my knowledge off of that.
1. So far, no. They do not damage embossing of decks as long as you are careful with inserting and taking out your decks. Dont forcefully jam them in there or pull them out with anger. Just take your time with it if you are having trouble at first and I'm sure it won't damage any sort of embossing in any way. It hasn't happened to me yet. Patience is key with card clips!
2. Going back to my answer with #1, it will leave scratches if you aren't careful with your deck. Treat your deck with respect! Sounds silly I know but take your time with it when you first get a Card Clip. You don't want to damage your card box if you are worried about that sort of thing. Like I said, patience is key. Don't get frustrated if you can't get it out. Don't jam it in either. Slowly slide it in.
3. Not sure on that one. I don't follow Dan and Dave's fancy edition card clips. I've had a regular edition, good 'ole Joe Porper clip for a long time and it's the same as it was when I bought it (minus a couple of scratches from dropping it on the floor). If you are going for style, by all means go for it, but you don't need to fork out the extra cash for the looks. Your spectators won't be that amazed by something that carries your cards (in all honesty). But hey, if you want it, more power to you.
4. Yes. All card clips scratch depending how well you take care of it. A card clip is supposed to take care of the cards themselves, so it's supposed to get scratched. Don't worry about it. If you're planning on getting a Carbon Edition clip but you don't want to get it scratched, you will get it scratched. Believe me. It will. It won't stay fancy looking for long if you plan on using it.
5. Depends on how much you use it. It should last for years, years, and years. And that goes for the regular edition Porper Clip, too!
6. I'm going to guess the same as all other Card Clips made by Porper, just a different style and look.
Hopefully I've helped out. If you have any more questions, please ask!