I've had my carpet for a number of years. Lost track actually. I haven't lost any fish in several years. Don't plan on it any time soon either. There are steps you can take to reduce the risk of fish getting eaten by a carpet.
1. Don't over stock the tank. The more crowded the
tank becomes, the higher the likelihood that someone will
bump into the carpet.
2. Don't stock aggressive fish or fish that don't get along. A fish
trying to escape another can easily make a wrong turn.
3. Always quarantine all new fish and feed them very well while
in quarantine. Fish that are week, stressed, or ill seem to end
up in the carpet.
4. Startle the carpet, causing it to retreat under its rock, before
placing new fish in the tank. This will give the new guy time
to learn its surroundings before the carpet comes back out.
I have NEVER lost a coral to my haddoni. I don't even think that's a legitimate concern. Once settled in, these anemones rarely move. Mine has moved once the whole time I've had it. That was because the MH went out, and the only light it had for two weeks was PC's. Even when/if they move, they don't move fast. You will have plenty of time to clear a path in front of it.
These are large carnivores like all large anemones. There is always a risk when mixing predator and prey. That doesn't mean we can't drastically reduce that risk. Every fish I lost to my carpet can be contributed to something I did wrong. As long as my fish stay healthy, and I don't do something stupid, I don't believe I will lose any more fish to my carpet.
To answer your questions. I, and many others, believe that resident clowns will help keep fish away from the anemone. Especially if you get large clowns like saddle backs. They may not keep all the fish safe by themselves, but I think they help.
I also think you should keep the anemone. If it is healthy and doing well in your care, passing it off to someone else may be a death sentence for the carpet. To many of these animals get purchased, the owner takes no precautions, and their fish get eaten. Then the anemone gets passed around until someone ends up killing it. These are not the evil blood thirsty animals that attack your fish in their sleep, like some people will have you believe. Fish can learn to live side by side with these anemones without harm.